That is a very cool sig. It's difficult to work with MSpaint, so I really admire those who can. =)
If you're looking for free software that does a lot of what Photoshop can do, I recommend The Gimp: http://www.gimp.org/ It's a lot like photoshop (it does take some getting used to)... the difference is IT'S FREE! That's right. Shareware. It's a good alternative for the graphic artist on a budget.