Currently the max allowed amount of characters in a signature is 255, while that may seem like a lot, it's not. The reason is that it takes into account the character used in tags. (Such as images.) This means that adding links, text and so on is near impossible if you plan on having a image. (I use URL shortners and I still have problems.) Increasing this from 255 to say, 600-650 for normal members and infinite for Otaku's and staff seems like a good idea.