The Paint module has always been the weakest part of ClarisWorks/AppleWorks. There are freeware paint programs on the Web that will run circles around it. GraphicConverter, which is actually a conversion program, has a simple built-in paint program that is infinitely superior.
If you want to step up further, find an old copy of Photoshop. You should be able to find version 3.x for $50 or so, and that will give you about 75% of the power of the current version for most purposes. For $150 or so, there's Photoshop Elements, which is OS X compatible in the current version.
Cheers :-> Bill