While some people do have some awesome video clips in their siggys, most I'm really not interested in seeing plus the videos occasionally kill pages for me which is super annoying. Is there a way to disable those somehow? I keep feeling like there must be but I haven't been able to find it yet.
they're not videos, they are gifs! what you can do is disable full forums in your site preferences. that will turn off all signatures and forumsets.
If they're the GifSoup ones, you should be able to knock those out with AdBlock, ironically.
Edit: Slightly ninja'd - or one could do as Potter suggested.

Ah, good to know. :) But will that eliminate just the clips or all images?
Turning off signatures will get rid of all of them, gif or not.
There is a program you can download for firefix which disables gifs I think, lemme find it for you:)
[edit]
It wasn't a download, pardon my mistake. But this page here tells you how to pause/disable gifs if you're using firefox!
this will turn off gifs for EVERY site you visit, not just Subeta.