First up is artist "vonplatypus" with a creative imagining of an early 1980s Choose Your Own Adventure book ... if written by Lovecraft. The design and illustration style nicely mimic the work done by Don Hedin (under the pseudonym Paul Granger) for those iconic CYOA books.
Vonplaytpus offers a couple of other CYOA-style covers — one with a Doctor Who theme and one with a Harry Potter theme.
Speaking of Choose Your Own Adventure, the greatest parody-tribute to that series might be 2013's Who Killed John F. Kennedy? by Justin Sewell and Despair Inc. The 190-page book went out of print quickly, though, and used copies are fairly pricey.
The second mashup postcard, above, is by artist "Ratigan" and places Lovecraft and his cuddly cosmic entity Cthulhu side by side in a tribute to the bus stop scene in Hayao Miyazaki's My Neighbor Totoro.
Doesn't it just give you warm fuzzies inside, seeing Old Octopus Face keeping his creator dry?