I’m not an artist. Really, really. Despite my not-very-good best efforts, I’m still not any good at drawing, or sketching, or pixel-art-ing. For The Dungeon, I pretty much used the Roguelike Tiles as best I could, and found pre-made GUI art elsewhere. I did some of the in-game UI border art in Photoshop, but it’s all pretty much not-me.
For Panic Attack, initially, I used a few things from Subtle Patterns, but eventually decided the backgrounds kind of clashed - so, I made my own. Not in Photoshop, though. Still not an artist, remember? Instead, I rendered graphics myself, procedurally. The non-pixel-art in-game styles are, actually, all rendered procedurally too. (For those keeping track, those styles are Default, Seven, and Seven Symbols). Up until Block Party and Block Symbols, Seven was actually my favorite style.
So! What in the hell are procedural graphics, anyways? Well, to me - and hopefully, to everyone else, too - procedural graphics are, duh, graphics (art, but not capital-A Art) you generate algorithmically. This means, someone who doesn’t really have the art skills, like me, can still have reasonable art and graphics without killing myself in Photoshop or Pixelmator or what have you.
And since I brought it up, Pixelmator is freaking sweet. I don’t know if I’d go back to Photoshop after using it, at least, for the pixel art kinds of things I do.
Procedural art is great if you have absolutely no art chops and enjoy lots of iteration.