I think we have settled on invaders from mars (similar to your idea), but this will be way beyond fretmarkers. I'm going to be doing a large planet Mars in the first three frets and them groups of saucers coming down the neck getting bigger as they near the body of the guitar. I may position the groups roughly around the fretmarkers positions, but I'm not going to let them influence the design. If I can play the Unicorn guitar, no amount of inlay on the fretboard would bother me.
That sounds badass man!