I normally don't do this, but I will be voting for one background in multiple categories.
Concept: abstauber
Playability: selmiak
Artistic Execution: abstauber
I think abstauber's background is the one best suited for the template. The rest are all very well done. If it were up to me rather than a vote, I'd choose abstauber's.
lorenzo: Both of your backgrounds are wonderful. I would relish the opportunity to work on something with such an art style. As others have said, the transition to low resolution did a disservice to the art, and made the backgrounds less suited to the Roger sprite.
Nixxon: I always love your use of color, but I'm just not a fan of the overly exaggerated cartoony look. And as much as the scene is interesting, and there is a lot of playability, I just didn't find it to be as suitable for the Roger sprite.
eri0o: I really like the piece overall, and it could definitely work in a game. It's a little bare, but the colors and concept are fantastic. The scale seemed a bit off for the Roger sprite.
Rocchinator: The concept of a ship's bridge is perfect for the template, and the work has some great colors and details. I felt the captain's chair was a bit out of place, and the overall image perhaps a bit out of scale, and so less suited to the Roger sprite.
abstauber: I think that this background is exactly what the contest and sprite needed. The concept of a ship's bridge is the best, and it looks fantastic. The colors set a mood, and the simplicity helps. There are clear exits and things to interact with. The Roger sprite looks perfectly at home here.
selmiak: I really enjoyed this background. Although these islands are floating in space, there is some semblance of gravity evidenced by Roger standing and the water falling. I love the glowing orb in the center, and the blue cup ship is a nice touch. I like that you went the extra mile to include exits and pathways, it really made the difference. This is a background that the Roger sprite looks ready to explore.