don't know paintshop pro that well, but I do know that there are some black skies in Bryce (Starfield, without the stars turned on, for example). There's even a white sky as well.
There's a Photoshop-like program (free) called the Gimp, that can do masks, layers, lassos, and whatever else you might be thinking of. It's googlabul..;)
It's also possibly to import a picture into the background as a 2d-plane, and render against that (cheat like a bandit; turn off the shadows from the sun, and from any lights you use..;) Just did it with my last pic. Hope this helps.

I wish I'd said that.. The Staircase Wit

anahl nathrak uth vas betude doth yel dyenvey..;)