I was actually already working on improving the greeting for the JFBCLogin module to be more similar to the core Login module, when Alex told me about this post.
The line of code to override (for mod_jfbclogin/tmpl/default.php) should now be:
echo JText::sprintf('WELCOME', $user->get('name'));
The language file (for en.GB_mod_jfbclogin.ini) will now be something like this:
For the greeting, the 3.2 release will update the greeting portion to 1) have an option to use username/name 2) show/hide the greeting and 3) make the login message more configurable like the core language file.
If you hadn't already figured it out, hope those snippets make it easier.