In addition to DPaint, also take a look at PPaint (should be included with Amiga Forever).
On the higher-end front, there's PerfectPaint (freeware), ImageFX (commercial), ArtEffect (commercial), and ADPro (commercial).
The big names in 3D rendering on the Amiga are Aladdin4D, Cinema4D, Real3D, Imagine, and Lightwave. Of these, I think only Aladdin and Imagine are still in development.
For structured drawing, take a look at ArtExpression and DrawStudio. There are a few others as well - DesignWorks, maybe?
For DTP, the answer is PageStream, hands down, no question.
Good luck, and have fun!
