I like the showgirl graphic

I understand that the dice are on one side and the girl on the other side of the cab? If so, I'd say give it a try and add shading. If the dice and girl are in the same visual field, then I have to go with RayB - try to match their styles.
If you are happy with the shaded showgirl, but the dice don't match you could go two ways:
1) repaint the girl
2) repaint the dice
Since a cube is fairly easy to shade you could add a slight darker tone of red to the sides facing to the left. I noticed shading in the flames too so there is some shading present in the image already.
So what would I do? I would probably go with the 'flat' look for this one. I also sense a retro feel in the Vegas graphics that I like. It would be very interesting however to see what the shaded version looks like ... hmmm, choices, choices...