I like the Toaster Chroma video effects, nice to show off some video stuff, if you like video you could do some green/blue screen effects with chromakey. Make an animation in Dpaint and insert yourself with chromakey.
The octamed runs on any Amiga, so no need for fast CPU.
As for demoscene, most new Amiga demos run on 060 or UAE, so it would be nice to have.