Apparently the photopass photographers shoot everything on auto. This is a bit concerning since it's expensive. They're not 'professionals' in the true sense of knowledge. I'd at least want an image I can post process for printing on canvas! You certainly need to clean images up and prevent 'clipping' (total black and total white that loses detail). They can look awful on canvas.
My solution was to buy a new DSLR that I can take with me, shoot things myself or put it in modes I want before handing it to a photographer, post-process the image and then have a great canvas print after. It's a lot of work though and takes a lot of time to learn but I think it's worth it. Got me into photography actually. Anyway, unless you are going to post-process the image, you may be disappointed in the results for canvas. Perhaps it's worth printing a larger photo instead?
Old thread but I just thought I'd mention it if anyone was thinking about printing on canvas from Photopass and since SnowWhite09 raised it.