Yeah, I'd have that artwork put on an original, if I managed to get one, but I wouldn't use it for a clone I've built, tempting as that is.
If you were to use the art one time on a personal pedal, you'd probably fly under the radar. I often see other pedal-builders doing that, using the artwork and even the name of the original pedal they've cloned for "personal" use — which may or may not be legal, I don't know — but then these builders sell off their personal pedal and of course must build themselves another to replace the one they "realise" they never should've sold. Some do it four or five times or more.
Needless to say, if you started building & selling clones or even just using the art on something else you were selling, that would not be cricket and you'd wind up in court or the very least a C&D letter would be dropped in your lap.
