What they said.
Also, the shoulders look a bit wide, but before slimming them, I recommend widening the hips.
With the legs, the thighs should be much longer, at least the same length as the tibia, but since it's a toony pinup you can get away with some exaggerated anatomy.
Overall, I'm actually gonna say it's biggest hang-up is the pose. The anatomy can be remedied, but I'd say focus on making the pose more provocative, more glamorous, more pinup-esque. As suggested earlier in the thread, spend more time researching pinups, maybe not just the classics, but also modern pinup photographers such as Lithium Picnic or those Winter & Wolf people. You may also want to take a look at
Rion Vernon's site, since his style is very similar to what you're going for, and see how he puts his pieces together. I believe he relies heavily on reference photos and then tweaks the proportioning and posing. By doing several rough sketches before sitting down with the lineart, you can get a better feel for how the finished composition will look while only spending a couple minutes on it.
Kicking up her left leg and moving her left arm and shoulder forward will add glamor and yet I'm not certain that'll save the composition.
confused Forgive me if I'm being too harsh.
sweatdrop