Years ago, somebody did one up where they put Rand's and Uhura's heads on some rather picturesque beauties for a Boris Vallejo-style cover like many done in the early-mid 80s for Trek books, titled Orion Slave Princess. I remember seeing it on AOL (I think). I just went looking and found a dead link, so it may be lost to the Internet aether.
And a few years back, the Trek Art forum had a contest to design faux Trek book covers, and one poster whose name escapes me created a handful of truly awesome covers like you might've seen on pulp fiction paperbacks during the 1960s. I've still got those saved somewhere, but I don't know who to credit.
