So as tazuras said while i was typing. You slice up your signature in equal parts, say a 700x250 signature becomes 4 parts of 350x125. Part 1 = top left, part 2 = top right, part 3 = bottom left, part 4 = bottom right.
This is my signature in BB Code. There is the first picture, the main one with -[SC]- at the top and a majority of the picture with my character, then I hit enter and put in the links in the right order with image and URL tags. After that I hit accept and they came together to form a signature.