Everyone has their own ideas about what sells, but since you asked I'll make one suggestion. Try to get an original looking face in the market place. There seem to be more real looking faces for M4 than V4 even though she has been out longer. Find a model or celebrity you like and spend about a week (yes a week) trying to get something like her out of your own morphs. Sink her cheeks, give her a chin dimple or a hook nose, just something more than the "There, I spun three dials in her morph package so pay me for it" look. I think those figures roll in and out of the marketplace with little attention anymore. After that get some kind of inventive skin shading package on the texture like bagginsbill's VSS that will really make the figure pop.

 

Good luck