Aphex Twin's Selected Ambient Works 2 was released in 1994, and it's front cover is the result of RDJ scratching the Aphex Twin logo onto the back of a leather travel case. The sleeve notes are another story, having been scratched into the back of a Yamaha CS-5 monosynth, which was later owned by an artist called Solvent.
In the above video Solvent talks about making an EP with the synth entitled 'RDJCS5ep' - which appears to be a promotional springboard for a subsequent sale on ebay (does anyone know a final selling price?). For those after more weird merch, how about a 'Come To Daddy' snowboard?
If you're interested in hearing about the origination of Aphex Twin art, check out this talk with visual artist Weirdcore, or the video below with logo artist Paul Nicholson:
Pre Sunroof gig at Superbooth
Pocket-sized synthesis & battery operated beats
Finding inspiration in a world of sounds
And a host of other features too