Great job! But I have to agree the back ground is a bit under done, but honestly I really can't say anything because my back grounds suck >< Still you've done a WONDERFUL job! What kind of poster is this for? An event or something? o.O
I really like this piece, and the retro-ness oozes out. The only thing that i would like further would be maybe some subtle shadows on the person, but that might take away from the line and color aspect of a retro piece.
i like a lot about this, and you definately got that retro feel. however, i hate to say it, but i think you might have gone a bit too subtle on the background.
the figure looks GREAT. she's standing on a balcony, is she not? i wish there was maybe just a bit more detail work in the foreground, like maybe another plane on that balcony wall. and maybe a bit more of a gradient on that skyline? i guess i just want a touch more dimensionality and contrast to her surroundings.
great color scheme though, and i really like the feel of the image. nice work!