Sorta like "buying Playboy for the articles", eh?
Anyway, while I don't recall having ever purchased an album w/ LP intact for the sake of the cover art, I have purchased "empty" covers for the sake of the cover art. Not many, but several.
Through 59 (including my) rplies to this OP, has not one person yet listed the infamouse EP:
Boss Hog
Drinkin', Lechin', & Lyin'
(Amphetamine, 1989)
Early work by Jon Spencer and (IIRC) then-wife (or galfriend) Christina Martinez, it is a great (and typical) "Spencerian" work which happens to be adorned with quite a memorable cover image, an example of which I'll not post here. I'll let y'all seek out the image @ The Google for your own amusement and/or enjoyment.