Here's a piece I recently did, the director said, "Like this Leyendecker painting, but different".
Sorry about all the text. I had to do that also, until I get real illustration jobs, I'm sure I'm stuck doing alot of that.
A couple of things about how I did it. I scanned the original image and cut and pasted to create the pose I wanted. I used that as a model. I created a grid and penciled it out. Then scanned it in, and back and forth with scanning and printing, adding coloured pencils. Photoshop and Painter.
One happy accident was when I was creating the "model" I used the magic wand to remove the background of the oval leaving an outline around the figure. I really liked the way it looked and incorporated that in my final image...
Oh and the oval and background lines are just cut and pasted then painted over.