Do you want to make custom themes for your profile page?

[Pika-duck 12]

Something that could make people enjoy their own account more would be a custom picture adder for your profile page. Something like a Youtube channel editor.

[Jokuc 8,172]

You can add a custom profile background by going to My Settings -> Profile Customization. If you mean like a profile banner, that's probably not going to happen and I don't even want the feature added. Alternatively you could just create a banner and add it as an image at the top of your "About Me" section. Customizable buttons and bars isn't going to happen either.