You can load upto 3 sigs at a time, upto 500 and they give you a link and everytime that link is called it shows a random sig that you uploaded
(you need an account to see links)
On a side note, Im giving +2 rep for a nice sig with my name, I want heaps, I have 3 on rotation, kinda want another 497....
Refresh the page a few times if you wanna see my siggy change....
Btw: this wont work on your avatar