The aluminum can is a good idea. The curved film plane does seem to give interesting results, from the two that I've shot, though I think it would be a much more pronnounced effect with larger format. It'll also be easier to load, as its a bit of a pain to line up a little piece of film with the pinhole in a 35mm can.
I'll grab some LF film or photo paper and try that. By the way, how did the pinhole prints on Cibachrome paper that you mentioned come out?