PhotoImpact doesn't support .abr files, but if you have Photoshop, you can convert brushes to pngs and then import them to PI. You can also make your own brush textures and stamps in PI to get some cool effects.
Here's a tut on using the stamp tool: http://all-in-the-image.com/pi/tutorials/tut3-1.htm
and check this thread for more info on making your own brush textures: Sanding Effect

HTH,
KayLynn