Edit Options, under Profile, gives you the option to turn off viewing of other user's signatures (and avatars, aka userimages).
The issue of images in signatures may require more deep discussion before a decision is come about the fate of them.
In my humble opinion, images in signatures are fine
so long as they do not take too long to load, are not huge, dimension-wise, and obviously, don't consist of porn.
Some might argue that images in signatures are unnecessary especially when avatars are available, and I will agree to a point that it does clutter up the thread sometimes when images are obstructive and invasive of screen space, but if someone wants to use acceptably sized images to spiff up their signature, e.g. to give links for people to contact them with, or just look pretty, then they're shit out of luck most of the time, because the avatars are single images limited to 90x90 and 24000 bytes, with no way to use the image as a link to someone's personal website or anything like that.
In any case, it will most likely just boil down to you guys asking me for a hack to be able to turn off images in signatures anyway
I'll look into doing something like that, and if it's not too difficult to do, I'll make it so. My experience with php as of yet is somewhat limited, but I think this may be something as simple as bypassing a code parsing for [ img] or < img if a switch in the user's profile is set to on.