Correct, we don't have an easy-tag for a custom image yet. In that case, you'll need to replace the Easy-Tag with the actual HTML. You can find it on the page below (there's multiple options):
www.sourcecoast.com/jfbconnect/docs/common-support-questions
In short though, the code looks like:
<a href="javascript:void(0)" onclick="jfbc.login.login_custom();"><img src="/linktoimage.jpg" /></a>
We're still investigating the Javascript login button problems, and will update you when we figure out what's happening and/or have a fix.
Thanks,
Alex