You can do like some people here do any turn off all sigs and avatars by going into the user cp
http://www.ahsforum.org/forum/usercp.php?s=
perhaps it's cuz of my DSL, but I've never had problems loading sigs, even when my DSL was utter garbage...lol... as I've said, it just depends on the filesize of the image, so think of it like this:
56k = 5-7kb/sec, so a 50kb sig (which I commonly use) should load, at most, in 10 seconds, regardless of the actual pixel size.