A project I always have fun with is my Clone Club Mystery Series. It's super fun and silly and I always have a blast plotting out the "stories", which are kind of an Orphan Black flavored take on Welcome To Night Vale's quirky, weird nonsense narrative.
I have yet to do a project specifically in this style because, well, no one's ever asked me. They're a vaguely popular series among a nice chunk of the fellow OB fans I interact with, I presume because they are a bit different from usual fan art and paint pictures of fun/weird stories that could be told in the Orphan Black universe. So I derive a bit of satisfaction from that! If I did do real book covers, I'd love to get a gig where I could do something in this vein. Something quirky and clever, maybe a little disturbing, minimal and eye-catching.
You can see the full series here, and below is the latest installment.
The best part about fan projects for me is that they keep the creative juices going, without necessarily asking you to invest a huge ton of time. With these, I spend maybe 2, 3 hours total conceptualizing, sketching if need be and then illustrating. I don't really intend these to be major projects. They're just little arts for the love of it.
In a vague way, projects like this one are my little nobody spit-in-the-eye to people who want to argue what is art and what isn't. From people like Euclase who draw gorgeous realistic renderings of actors and TV or movie characters, to skilled and established artists like Dan Matutina or James White who create the occasional piece based in a TV show or film, I don't think there's any real place to argue over what is creative and moving to someone when all of it has equal potential to be. Unless, of course, you talk on a more technical, law related level, which Fan Art Is Fair Usage is currently tackling. Check them out, they're doing something interesting.