Creative Resources would probably be the best place for these sort of discussions, since you're seeking input on a creative/artistic project from other members. Just post as much as you have in mind for your OC, and other members will be more than happy to weigh in their opinions and advice while helping you fine tune and refine what you already have in mind.
From my experience, the best place to post any sort of MLP analysis/ review videos would be either through a blog update, or you can alternatively create a thread in the 'Other Fan Works' section in Octavia's Hall if you're looking for critique on the video itself (and so long you are the original creator of the video). Posting these anywhere else, including Show Discussion, may result in your thread being either locked or merged, since there's most likely already an existing thread pertaining to whatever topic you're reviewing.
SkyBound's post in Where do i put discussions for OC's? was marked as the answer