Yes and no.
I'm fairly certain you can't. However you can install
beryl, which is a fork of compiz.
It has a theme manager called emerald.
While there are currently no official beryl rpms for fedora 6, some have been submitted for review
here.
Only srpms are posted, but I was able to build and install them just fine.
after, you just have to start it with beryl-start.
It won't interfere with compiz, so you don't need to worry about that.
Good luck
edit: location of beryl rpms can be found in this
post.
Though it helps to know what they are good for in the first place
