The only "junk" you should clear away are topic files and
graphics that you are ABSOLUTELY sure are no longer used. I
wouldn't rely too heavily on the Unused Files Report, though.
RH uses a lot of project files to keep track of everything it
needs to do, based on your instructions (intentional or not). These
can range from HTM files through XML files, APJ files, etc.
Unless, of course, you're bored and you
want to recreate or recover all the things you cleared
away...
Good luck,
Leon