@Princess Crow;

It sounded strange to me that our limit was so small. So I had a quick look. The forum rules say the following:
Member signatures have the following restrictions in place:

Signatures, including images and spoilers in the signature, must be a maximum of 250 pixels in height and 600 pixels in width.
Images used (animated or non) cannot exceed 500kB in filesize.
However, if you want to upload your image to our forum (like an attachment) in order to use it in your signature (I didn't actually know that was possible, and I'm not sure if the option should even be switched on, but anyway...) then you are restricted to 100x500 and 9.8KB. I assume this is mostly because the images are being uploaded to our server and therefore using our storage space, so we probably don't want to increase the limits. But if you upload the image somewhere else (tinypic, imgur, imageshack, photobucket) and then add it into your signature using the image link, you are allowed an image up to 500KB. So I would suggest you go down that route instead. :)