Many Joomla! web designers have experience with offensive spam registrations. Very annoying for all of us. Here is one of the solutions how to avoid it. By using Registration Validator plugin for Joomla!
After installing this Joomla! 1.5 native extension, you can block unwanted user registrations by blocking email addresses, domain names, usernames or IP addresses. This plugin is tested in standard Joomla! user registration, Virtuemart, Community Builder, JomSocial, CBE and Ajax Registration.
Joomla! Registration Validator Features
Can anyone provide a few suggested template galleries for Joomla?