It shouldn't be too big, it is within the maximum size for a signature!
I resized it but it's a little blurry now.
Maybe that works better.
(And I promise to make smaller siggies in the future.
)
Edit: Maybe this is a stupid question, but are you sure it is the picture that is too big or did you try to put in writing which made your signature (including the picture) more than 50 characters long?