Paint work is very fickle. If you can find the perfect buyer who loves the shots to death, they might pay a lot for them. As a painter myself, I actually subract value from a lot of minis if they're painted, because I buy to paint, then field in my army in my own colors.
You could try to sell me a limited edition UK White Dwarf Subscription Marine Sergeant painted by Todd Swanson, but if it's in Crimson Fists colors, it's worth only as much as the base model, to me. I play Ultramarines, and don't need a single Crimson Fist in my force. He'd see the inside of a jar of Simple Green
One thing that could potentially boost the sale value of the lot as a whole is including a written list of all paints used in their manufacture. That way a prospective buyer trying to start up an army from scratch can replicte it at least in tone and color. Of course, that's a lot easier to do when you're the one who painted them originally.