Why not use Quartz?
I've used this on XBMC in the past, not sure if it will work with RasPlex, will give it a try tomorrow.
http://img804.imageshack.us/img804/2128/screen7h.jpg
RasPlex uses a port of "Plex Home Theater" (aka: PHT) running under OpenELEC Linux.
As you might expect PHT and XBMC are not directly compatible when it comes to skins.
Some skins have been produced with variants both for XBMC and PHT, but the latter are not stable.
This is no slur on the workmanship of those 'skinners' but is inevitable as PHT itself is an unfinished product.
Until PHT gets a stable release, with open info on its skin requirements, there can be no fully stable PHT skins.
(Apart from the original 'MediaStream' skin that it comes with, adapted to the current PHT changes.)
And since RasPlex uses a port of PHT, it too suffers the same limitation.
There are a few experimental skins around, but expect glitches and failures if you try them.
Such problems are to some extent inevitable as long as the PHT design itself is changing.
However, all is not as hopeless as the above may make it seem.
There is one skin which is working quite well with the latest PHT release, and that is the "Night" skin.
(You can check it out in the subforum for skins.)
I' don't really know how/if this "Night" skin performs with RasPlex though, since RasPlex uses an older PHT version than the latest PlexPass release...
There's also the risk that some alternate skins use too much 'eye-candy' to work well on a relatively slow platform like the RPi.
Best regards: dlanor