You would be limited by the Zorro II bus, both in bus speed and the cards available for it. The bus speed is not that big an issue in most cases. I really don't notice a big difference in the graphics speed between the EGS Spectrum in my 030 A2500 and the Cybervision 64 in my 060 A4000 when running Workbench but the difference is dramatic whan I'm running CPU intensive operations like painting with complicated brushes at high resolutions. The faster CPU is the main factor but the 32 bit bus helps when there is lots of graphics data being moved.
The best RTG cards--Picasso IV, Retina Z3, Cybervision 64 and Cybervision 3d, are Zorro III, and you won't be able to work in 24 bit beyond 800x600 SVGA with a Zorro II graphics card. Even with my Zorro III Cybervision 64, 24 bit 1024x768 is a bit touchy and works much better in some monitors than others.
I don't think you would complain very much about the performance of a Picasso II in an A2000 with a Blizzard 060. Until last year, I had a Picasso II in my A4000/040 and the Zorro II bus speed would be the same in both setups. Now I have a Zorro III Cybervision 64 and the graphics speed doesn't seem faster on a perceptual level but I now have 24 bit XGA and 16 bit SXGA which I didn't have before. I recently replaced the stock 3640 CPU with a Cyberstorm 060/PPC board. I'm just beginning to play around with software that uses the PPC processor but the 060 has made a huge improvement in what I've already had installed in it. I'm especially noticing the difference with the image processing and rendering functions of ImageFX.