You can just PM me and I will create 1 for you if you want an avatar. I can do plain and animated. (I don't know how to do glitter text yet though.) If you wan't a animated avatar make sure it is 64x64 pixels otherwise the animation won't work. If you want just a plain 1 you can make it any size I think it re-sizes automaticly.
For signatures the maxium size is 500x200 pixels
(or 10 lines of text if you just have text on here.)
For profile pictures the size is 250x250 pixels. I don't know how to do animated profile pictures but I have seen some and I think they have their profile pictures set as like 240x240 or something.
Hope this helps!
~ Charles 
Example (here is my signature on TTC I have text to go along with it also so that is why it is so small.):
