1) you should have an actual model with a light source if you want to emulate his work.
2) Use oil paints - or find out how to achieve the same effect with digital.
3) stronger shadows, more whimsical hair, garter belts, more schlera (white of the eye), warmer skin tones (unless you want the pale haired, dark skinned beauty - which is just fine), and I would make sure to show more torso. Also have the model doing something other than sitting there looking at the viewer.
I think you should have more values by the eyes, and give that woman a warm, inviting, totally 50's toothy smile!
What you have doesn't look bad, in fact with a background, it'd be quite alright. But if you're looking to get to Gil Elvgrens style, I think the changes I've mentioned are legit. They may not get you completely there, but it'll help.
Doctors heal you, Artists immortalize you.
"Those who can, do. Those who can't, teach" - bullshit.
The usual staples for anatomy: