Adam is completely right... With freelancing in almost any industry, you're going to have periods of feast and famine. When work is available, it's usually quite plentiful, and at that point it's best to accept as many jobs as you think you can handle. I've had times when I've gone almost two months without work, and if I haven't saved up a good chunk form previous jobs, my wife ends up paying for everything (and that tends to make her a little irritable
). You can start to burn out, working such heavy loads, but after you finish a big run like that, you can usually afford to take a little time off. As Frychiko mentioned, working in-house is much better for your stress level than freelancing. I live in the middle of nowhere, so freelancing is the best option for me, now.
In way of pricing, I tend to keep my rates between $20-$30/hr, depending on the client. Having a static rate is rather foolish, because a lot of your work is going to come from independent developers, and often their budgets are very limited. On the other hand, if you get a job from a larger developer/publisher, they can usually afford more, and will ask more from you in return, so you don't want to sell yourself short.
You can get salaried positions, if you're willing to relocate, or happen to live nearby to a development studio. Again, pay can vary, depending on the size of the studio. If you're looking for in-house pixel art work, I'd say your best locations for looking are in the SF area, in California, or in Great Britain. Lots of little studios seem to be popping up there (along with some larger ones) and you might get lucky.