Hmm, this is a tough one to call. It feels like one of those months where I could keep arguing with myself to change my mind about the vote if I don't force myself to pick one.
Charlotte: As Atto said in the wips thread, this has a fantastic feel of a pulp book cover. Even the composition has the space and balance that's just waiting for the title and author name. The whole sky is nicely done with the starfield and those lovely textured moons, and I think the colour scheme is handled really well for a night/space scene. The subtle variations show all the different surfaces and subjects without breaking the muted saturation that is necessary for these scenes.
The alien structure acts as a great focus for the image by extending up through the horizontal layers of depth while also contrasting with the smaller details at its base to give a sense of scale. The whole landscape makes me think of No Man's Sky and if that was a 50's novel rather than a video game then this would be the cover.
The one thing that could add to the image is more contrast. Even a simple levels adjustment could push the lights a little more to give it a bit more punch. Which leads in nicely to the other picture...
Bender: Always nice to see a new face entering a challenge.
And as I've just implied, the impressive thing about this pic is that initial impact. The bright light and the deep silhouettes hit you straight away and even with that stark boldness the structure and its space reads well to the eye. It makes me think of those shots in Battlestar Galactica when the Viper ships launch at great speed, pushing the pilot back in the seat.
I love the technical angles and edges of the marks here, the sheen and saturation make it look suitably futuristic and that suggestion of a wormhole in the glare gives a context to the environment.
I think a bit more reflected light in the darker foreground areas might work well, particularly in a different hue to that dominant blue/cyan, but I know you were racing hard against the deadline.
But even without that it still looks like a great piece of concept art waiting to be passed on to the modellers to build into a 3D piece.
Sooo, which to choose. Hmmm....
As I said at the start, if I were to pick tomorrow I could change my mind, and the day after I could change back again, so I may as well make a decision now.
I'm gonna just lean towards Charlotte. Just. To me that pic looks a little more "Alieny" whereas bender's could just as easily be a futuristic, man-made structure. Charlotte's looks more "not of this world" and the more I look at it the more the subtle details imply that alien nature, plus the nostalgia of that pulpy style is appealing to me right now.
So... Charlotte. Just.
And an extra mention for Banj. Sad you didn't finish, I was enjoying its progress and would have been more than happy with any of those wips. And the fluffy clouds inspired me to put some rather less impressive clouds in my own picture.