Originally Posted by ultima88
Try using the Magic Eraser tool, it removes a specific background from the picture that's all the same colour. Say if the whole background was white, and you had a picture in the middle with a black border, and you used the magic eraser it removes the whole background so you only have the picture in the middle, Although I'm not sure if you need the background to be transparent if that's the case then you may need to recreate the sig (to get the magic eraser if you use photoshop, right click the eraser button and choose magic eraser).
You should also try and not use the whole 550x250 as some people like to put text underneath them, if the sig takes up the whole requirements they'll get taken off. Try using more of "400x150 or 450x150" they're not too small and not too big, plus the bigger sigs that have more graphics creation in them tend to be over 50kb if they're above 500x200px size. If you use simple pictures the filesize wont be a problem, but if you use fancy effects such as gradients, layers, borders, picture effects, you'll most likely have to resize the picture.
You need to read the requirements of signature making here and your sig has been removed because it is over the limit of 50Kb. You'll need to try and sort out how you do your sigs because if you continually try to use a sig over the limits you'll have your rights taken away from you. And then you wont be able to use a sig at all.