MorphOS transparent decals with a Morpho and the wording MorphOS would be nice for MacMinis and Power Mac cases, and maybe even for covering over the Apple logo on PowerBooks - so the light shines through and light's up the decal.

I'm not so sure about keyboard decals, as they are likely to come off, unless you can source a really good product that stays where you put it without peeling off.

I hope your hard work pays off as well.