Excuse me, but I believe the purpose of the signature limits are to reduce strain on the server, first. Also they are there to stop screen-spanning images from clogging up people's viewing of things. 500px for width is a good limit because some of the fixed-width skins condense signature space down to a rather small amount, and things beyond 500px either get shoved to the line below, which screws up aesthetics, or extends the post section of the poster, which is irritating.
If someone were to let you bend the signature rules simply to put your entire team in your sig, it would inspire many to complain "Oh, that person can do it, I should be able to."
That all being said, the problem with the new B&W sprites are that they are rather big for signatures. However, this can be remedied by stacking them up. 4 on top and 2 on bottom is a nice setup, as is 3 on top and 3 on bottom if you like symmetry.