When implementing Facebook Connect, in an ideal world we’d replace Facebook’s standard blue Connect with Facebook button with something prettier.
Unfortunately, it’s against Facebook’s developer policies, which state:
You must not circumvent our intended limitations on core Facebook features.
The Facebook Connect button is intended to be rendered in FBML, which means it’s only meant to look the way Facebook lets it.
However, it is possible to customise it to some extent. You can change the size, and the text. For example:
Visit http://fbrell.com/xfbml/fb:login-button and play around with the examples there, then press Run.
The possibilities aren’t exactly endless, but there’s a bit more scope than plain ol’