Hi,
It is fairly easy to add custom user profile properties using built in functionality, but implementing search for those properties would require custom development. The custom properties are stored as key value pairs in the mp_UserProperties table which makes them a little less convenient for querying than the standard properties stored in mp_Users table.
By default we use Gravatar for user avatars which allows them to use the same one on lots of sites, but you can also change to use the internal Avatar system from site settings, then users can upload/crop one image, not multiple ones.
Hope that helps,
Joe