bash rename script

I need a script to rename files. It needs to work in the mac osx terminal. There are 100 files in three levels if directory. In each directory there are 2 files: parent_directory/user-a/avatar/[login to view URL] parent_directory/user-a/avatar/[login to view URL] parent_directory/user-b/avatar/xxx XXX [login to view URL] parent_directory/user-b/avatar/xxx [login to view URL] the files are irregularly named, some with spaces in the filename, some are JPG some jpg I want these two examples to be: new_parent_directory/user-a/avatar/[login to view URL] new_parent_directory/user-a/avatar/[login to view URL] new_parent_directory/user-b/[login to view URL] new_parent_directory/user-b/[login to view URL] ie. They are in a new parent directory, with the same user directory, with no 'avatar' directory, with one image [login to view URL] and one [login to view URL]