If you're a student (or know one who's willing to help you out), you can get the Adobe Creative Suite from JourneyEd.com for about $380. It may seem a little pricey, but keep in mind that it contains Photoshop, Illustrator, and several other programs. I have it and I'm quite pleased with it, and it's way cheaper than just buying it from a typical vendor. Illustrator is great for drawing things or tracing them, but for image editing Photoshop is the way to go.
And to answer your question about Sub-Zero, I based my drawing off of the MK: Deception version, so that's why he looks slightly different from the "classic" version. ;P