For what it's worth, Paint.Net is a great program for those of us who don't have Photoshop and don't like MSPaint. It's free, and it's far superior to MSPaint. And it supports layers, so you can have your collision mask in one layer and your background in another.
haha yes! I use PDN too
I do have PS, but PDN is good for quick, simple things, as PS take forever
to load. Also I like the less cluttered PDN, and I had PDN before PS so I'm more accustomed to it.