Sorry to interject something hyper-negative in here, but I would say that
there's nothing particularly special about IDM cover art when compared to
most other genres... Sure you have some rather decent designers and visual
artists out there (DR, Me co, Wolstenhome etc), but brilliant design and
innovative packaging are things I see just as much outside the genre as
within.
The only thing I see more of in IDM (and dance music in general) than
elsewhere is a crop of ugly, mac-lazy, I've-got-KPT-and-I'm-gonna-use-it
sleeves.
Of course, if we're talking about stuff that's "trippy-lookin'" instead
of stuff that's well-designed, then I take my comments back :)
Peace,
Matt