valete

Hiya Freeze-Frame, and welcome to the forums!
 
I just want to redirect you to a couple of helpful links that may be useful when it comes to getting and setting signatures within this community.
 
First off, here are a couple of tutorial threads if ever you want to make signatures yourself. These tutorials are not the only ones in existence, but they are beginner friendly, and they feature step-by-step procedures coupled together with screenshots to guide you.
 
1.) Tutorial by ~Starlight~
2.) Tutorial by Jokuc
 
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We also have a Requests Guild in which you may find various request shops that may feature free signatures. 
 
To request for a signature, just post a reply within any of the open request shop threads available that specify that they are accepting requests for signatures. Each signature maker has their own guidelines on what they want each requester to include in their request (ex. size, specific vectors to be used, other details, etc.), so don't forget to take note of those as well! 
 
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  Now, there are other important guidelines that you might want to take note of first before making a signature yourself or even requesting for one in the Requests Guild.    For general rules and regulations concerning the signatures used within MLPF, check out this FAQ article.    Oh, and if you need a guide in setting up your signature, check out this set-up guide made by Moon Moon!

I've snooped around a bit, and I just realized that "Gravatar" is utilized in both MLPF and Pony.fm. In MLPF, however, there is an additional option. It is possible to upload and choose an avatar from your computer, but I digress. You probably knew that already!
 
Anyways, to change your display picture in Pony.fm, go to gravatar.com and sign up for an account. Make sure that you use the SAME EMAIL that you used when you signed up for Poniverse! After you upload a picture to gravatar, it should be available in MLPF and Pony.fm. However, as stated earlier, your display picture in MLPF does not have to use gravatar, when compared to Pony.fm (I.e. Your display pictures in MLPF and Pony.fm can be different from each other!)

It would be best to personally contact and ask Feld0 for anything related to putting up advertisements or selling things within the forums. He is the one who handles financial matters, and everyone who successfully posts anything (that isn't taken down) to gain profit here asked for permission first before doing so. 
 
You can go ahead and send him a PM for inquiries.

It is allowed to post links to your websites in your signature and your profile. To quote CD on the matter:
 
"In your signature, and in the designated 'website' profile field are the best and only real places to freely advertise whatever sites you'd like." - ~Chaotic Discord~ (2013, December 25) (Source)
 
However, if you'd like to start a thread about your website, it would be best to personally contact the administrators to ask for permission first. To quote Feld0:
 
"Permission to advertise is something you need to seek from the admins privately." - Feld0 (2012, May 10) (Source)
 
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Usually, I think the advertisements with the intent of profit are the ones that are not allowed within MLPF. 

I don't think they're erased or changed (just like how former donors/subscribers don't get their avvies and sigs suddenly shrunken).
 
If anything, I believe that you will just be limited in terms of receiving any more private messages, that is, until you have less than 250 of them.

There are actually a good number of users here who take requests for signatures! You can find their request threads in the "Requests Guild" sub-forum over here:
 
http://mlpforums.com/forum/97-requests-guild/ 
 
To request for a signature, just post a reply within any of the open request shop threads available. Each signature maker has their own guidelines on what they want each requester to include in their request (ex. size, specific vectors to be used, other details, etc.), so be sure to take note of those as well. 
 
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Now, there's also the option of making one for yourself, and this might seem like the better option for some who may want to implement more personal and/or specific details into their sigs that may not be necessarily easily communicated to other people/sig makers. 
 
Luckily, there already exists a couple of tutorial threads that may help you in making these yourself. 
 
Here are two examples of existing tutorial threads: 
 
http://mlpforums.com/topic/62260-how-to-make-a-simple-signature-and-avatar/
http://mlpforums.com/topic/8630-signature-tutorial-for-beginners/
 
These aren't the only tutorial threads in existence, but they do provide quite a detailed step-by-step guide that may be useful for beginners (in my opinion). 
 
 
I hope this helps! 

Right now, I believe there are two main kinds of clan discussion. 
 
The first kind of clan discussion pertains to the clans that are made in various games. These 'clans' are basically groups of players or bronies that band together in groups in order to have a better experience in-game. Depending on the game, these 'clans' may bring about different effects to those who join them. Most of these effects, however, entail the general experience of being in a brony community while playing a specified game. The creation process of this kind of clan also varies depending on what game you're making the clan for. 
 
Some examples of threads that discuss this kind of clan can be found in the links below: 
http://mlpforums.com/topic/38698-clash-of-clans-brony-clans/
http://mlpforums.com/topic/439-want-to-join-a-spiral-knights-pony-clan/
 
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The second kind of clan discussion pertains to a bunch of clans created with the purpose of having a 'clan war', which is really just a friendly competition that revolves around mechanics that entail getting the most votes for a certain clan that you support. 
 
The thread with this 'clan war' can be found here: 
http://mlpforums.com/topic/81070-what-pony-clan-do-you-chooseeverponys-vote-needed/
 
If you would like to add a clan to this thread, I believe it would be possible to do so by notifying the OP by posting in the thread itself, or by sending him a private message. 

According to Feld0, the recommended profile background size is 1920 x 1200 (pixels). 
 
This question has actually already been discussed before, and it can be viewed in detail in this link: 
http://mlpforums.com/page/faq/_/site-problems/i-have-some-questions-regarding-profile-backgrounds-r76
 
Additionally, the file size limit for regular members must not exceed 255 kb. You might wanna keep that in mind when exporting your resized photo/background.  

Good news! There are actually a couple of threads about this that already exist! 
 
The general directions in beginning a roleplay in this site can be found in this link: 
http://mlpforums.com/topic/6531-the-roleplay-world-system-read-this-first/#entry149599
 
I'll throw in this link too. Here, you'll find some of the terms we use in roleplaying, and also a couple of tips about roleplaying in general. 
http://mlpforums.com/topic/6539-a-general-guide-to-roleplaying/
 
 
If there's something that you still might be wondering about roleplaying, you can also check out the FAQ right here. 

To add the main picture of your OC in the character database, simply click the "choose" button when creating an OC, then navigate to where the file is on your computer. 
 

 
 
Once you've found the file, click it and press "open". 
 
 

 
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To add additional pictures that are related to your OC in the character database, you may scroll down to the field that says "other", and place it there. To add photos to that field, click on the add image button (shown in screenshot), then paste the link to the photo that you would like to add. 
 

 
If you're wondering about how you can upload your own files into this field, then do not fear! You can just upload the file/s you have to image hosting sites like imgur, then you can get the links from there once it's already uploaded to the internet. 
 

 
Additionally, you may add multiple photos and descriptions into the "Other" field if you wish. The screenshots above might not seem to apply to mac users (since I'm using windows), but the process should be similar. 
 
When all has been done, click save to finish! 

Unfortunately, the mobile version of the site is probably the 'lightest' version available at the moment. An official mobile application might be a solution to your problems, but we aren't sure yet about when that will come into existence. To quote Feld0 on the creation of a mobile app,
 
"An app is something we'd love to make available someday; unfortunately, our development resources are not unlimited, and are better put toward developing web applications that will run on anything with a web browser. These things cost time and money to make, neither of which our dev team has in unlimited supply. If anyone's interested in financially sponsoring the development of an app, it could happen sooner." (Feld0 - March 28, 2013)
 
Source: http://mlpforums.com/topic/53383-ios-app/

If you need a thread to be moved, I'm pretty sure the mods would help you do so if the reason or circumstance given is valid. Next time, to alert the staff about things like this, you can report your own topic and give your reasons there. That, or you can wait until one of the staff notices that your topic is out of place. They'll usually move it for you even if you don't ask!