Has anyone ever thought of using the hydrographic method to coat keycaps?
Might be a bit pricey but if it's possible you could get all kinds of patterns on there, plus you might be able to put some of your crappier looking key caps to good use 
)
I've thought about it -- whenever I see keyboards like this in stores:
I figured that's got to be done via hydrographics OR maybe a printing method that holds the entire keyboard and keys together as a set. Most of these keyboards look to have a chicklet sort of key, so that the graphics aren't thrown off by the topography of a keyboard with, I dunno, more "vertical" profiles? But I think it could work so long as the image you're transferring isn't too complex. Maybe a repeating pattern, dollar signs, skulls, etc.
Also, the above keyboard's imagery is pretty distracting, no?
I don't know of anyone who has done it yet, but they sell kits for people who want to camo up their guns, so give it a shot.
