Theymos - Please retract this policy.
The signature graphics are a fundamental part of the community. They allow a means of visual expression in what is otherwise a dull text world. Some bars are ugly, some are cool, some are informative, some are annoying. Whatever... they are expression, and the forum is made better for it.
Not to mention, the sig bars add tremendous ability for businesses in the bitcoin world to get some awareness. Personally, I really like finding out about new businesses and sites in the sig bar graphics. They help seed new ventures, and cross-pollinate ideas. Again, some are annoying or useless, but that's part of the package.
Net-net, sig bar images make the forum better. Removing them is a very bad idea and damages what some of us here enjoy as a very strong and dynamic community.
Please reconsider.
Another +1 from me.
This is a heavy-handed way of dealing with something that is at worst a minor annoyance on the odd occasion. Why not allow individuals to choose for themselves to display signature images or not? This is much better than a totalitarian ban, and I think you would find most people would leave them on. It's would be trivial to implement - slush has already suggested a way of doing it.
And DEFINITELY do not ban embedded images within posts. That would be signing the death warrant of this forum. Who the hell wants to frequent a text-only forum that bans all forms of imagery? Last time I checked, this was not the Soviet Union.