Tom... don't get rid of signatures. If you need to only allow sigs for people above a certain rep, in order to defeat spambots or to offer a perk to those that have been here for a bit then that's fine. It shouldn't be too high a requirement though, perhaps 500 rep, or less even.
We do have rules stating what can go into a sig and how big it can be, because the old forum was getting pretty cluttered with big sigs. After the rules were put in place it wasn't too bad. And if people don't like sigs they can always turn them off, yes?
At any rate, I do think people need a way to show off their stuff or link to their social networks or blogs or whatever, and a sig is pretty much the best way to do it. To get rid of them entirely is a bit drastic.
Having no sigs will be really crap.
90-120 pixel limit should be more than fine...
The rules state (and have for some time) that your sig can be no more than 90px tall.
You need to shrink your sig down a bit, mister! Come on, now... you have to lead by example <img src="smileys/smiley4.gif" border="0" align="middle">