Sizing guide for sigs and avatars
185 x 500 (w & l)
I've only just today put the sig limit in place. It still means a fairly decent size for sigs, but will mean contraints on the height. I think this is reasonable as tbh having huge tall pics in your sig isn't easy on the eye. Far better they run across the screen than down it.
2 links per sig is the limit.
Maximum font size is set at 200%.
Maximum character length is 450.
100 x 100 pixels and 50KB size wise (51,200 bytes)
This allows some leeway for moving gifs to be used in avatars. But please don't go overboard with the use of them as they can get annoying for others viewing threads.
If you wish to disable seeing sigs you can go to
User Control Panel > Board Preferences > Edit Display Options
and change what you see in there.
Hope this helps.