allowing animated gifs sounds like it could be good... i probably wouldn't use that feature myself (can never be bothered to put one together!), but i would question the 4Mb limit...
i have a super fast internet link, but others don't. When viewing a thread with 10 posts from different people, if everyone had a 4Mb avatar, you'd have to download 40Mb of avatars alone! That could render the forum useless to people on slow internet links (at least until the avatars are in their cache). It *could* even put off new people!
Also, I don't know how resizeable animated GIFs are in an automated system... maybe they work fine, but animated gifs are rather more complex than a regular gif. Anyway, if resizing isn't an issue, perhaps 100 or 200K should be the upper limit... you have to think worst case - even 10 times 200K would be a 2Mb download when viewing the wrong thread!
Anyway... i'm certainly not against the idea, just saying there are some technical limitations and usability limitations that may cause the feature to remain non-existant despite everyone wanting it... sorry to put a *slight* downer on it!
Done correctly, it could work really well (assuming automatic resizing is possible, of course)!
