I use postworkshop 3 to modify renders (and photos for that matter) with a painting effect for printing on canvas.  The results can be stunning.  PWS 3 has many, many filters to simulate the look of different painting, drawing and other media.  The new interface took some getting used to, but it's a lot of fun.

If you really want to get under the food, there is a node GUI allowing you to modify and create your own filters.

They have a free demo with limited number of filters, but it lets you play around and see if you like it.

I find it immensely easier than Photoshop and I have never been able to approach the same results with art filters in any Photo Editor.

Klebnor

Lotus 123 ~ S-Render ~ OS/2 WARP ~ IBM 8088 / 4.77 Mhz ~ Hercules Ultima graphics, Hitachi 10 MB HDD, 64K RAM, 12 in diagonal CRT Monitor (16 colors / 60 Hz refresh rate), 240 Watt PS, Dual 1.44 MB Floppies, 2 button mouse input device.  Beige horizontal case.  I don't display my unit.