First off, the colors, composition, and subjects are all great.
The designs and lines in the background add depth and an atmosphere, as well as a give a neat quality that really compliments the characters.

All of the problems, and the incredibly few problems, rest with these characters. I love the overall style and appearance, but there are some anatomical issues. The girl's head is a bit too far to the left (ours) of her neck, instead of giving the impression shes leaning a bit, it seems misplaced. The lineart on the man's hand, the one in her hair, is a bit too scratchy and inconsistent with the rest of the piece, and it seems a bit too small.

Despite these two evident problems, I really find this a great cover. It captures lots of personality and is very eye catching.
Great job!