You can upload custom images that you'd like to use for each provider to the /media/sourcecoast/images/provider/ folders. Add an image for each provider that you want to change. Then, in the JFBConnect -> Configuration area, you can select the new image you added as the default.
Beyond that, you can also call each of the login functions with just a line of Javascript. With that, you can create completely custom buttons with CSS and text or whatever you want to make 'clickable'. If you need info on how to do that, just let me know, and I'll gladly help.
Thanks,
Alex