What a beautiful boy, he's a cutie! But yeah, it is a
little big for a signature

Have you considered cropping it and adding it to your profile page instead? Click my username to see my profile page. Also, you could crop and shrink it to make it your avatar so it appears on all posts, but under your name. I took the liberty of making an avatar from the image, in case you were interested. If you want to use it, go to your UserCP and enter the url to the image in the custom avatar field.
Code:
http://www.3fatchicks.com/forum/andrew.jpg