Actually, I am one step ahead of you. I have a local -r1 ebuild, which I have not yet released because I am still trying to successfully add PNG support into it. For some reason that is still failing. Also, I had already added a proper description :P Anyway, thanks for noticing. And thanks for making a bug-report -- I now have xv on an official TODO list :)
*** Bug 2148 has been marked as a duplicate of this bug. ***
ok, so the description was added to the old ebuild by bangert@gentoo.org I have since released a new ebuild with the help of NAZ (from #gentoo) to patch up xv for png, jpeg and tiff support.