It seems that I can already imagine the flashing animations, big Comic Sans Letters and RGB action in signature, replicated by x amount of users.
I'd much rather see very small images allowed in signatures. The current 4000 character limit produces HTML signatures up to 15 kB, while the artwork still fails in many browsers. Allowing 2 kB GIFs at the cost of 1000 characters would be a nice feature. Maybe for the next Rank if we ever get one 