This is a rough edit of my first attempt at a retro/pinup style photo, and I would be interested to hear what I got right and what I wrong with it. Your feedback is greatly appreciated! thank you.
The pose, costuming and effect of air-brushed smoothing, are good for a retro look. The shaped background shadows and highlights, OTOH, somewhat suggests modern rather than "retro" to my eye.
Unless you are sold on the color cast (to my eye and display) as somehow retro, I'd suggest adding some magenta and red.
Thank you! Yes, I am not sold on the background either but the original just seemed uninteresting, so I tried something different. The color cast is there to tie her into the background, it looked too "cut out" without the cast. Of course, now that you mention it, its all I can see. This is the original for comparison.
This is very subjective, here's my 2 cents anyway.
To me, the solid colour costume contributes to a "modern" feel, black gives me a particularly "modern" feel too compared to other solid colours. So for the costume I'd go stripes, dots, coloured trimmed, or anything that is not solid coloured. To me these colours give me a more retro feel: turqoise, orange, cream, pastel colours, and etc. But I can see why if you want to avoide "cliche" look.