What kind of customizations are you looking for? The text for the login button is found in the com_jfbconnect.ini file and for the logout button, the text is in the mod_jfbclogin.ini language file.
If you want full control over the looks of the Login button (custom image, just a link, etc), check out the first few topics on the page below:
www.sourcecoast.com/jfbconnect/docs/common-support-questions
Hope that helps, but if you need something else, just let us know.
Alex
Custom login button
