I'm going to get a couple of images printed out onto canvas using one of those online things where you just upload a photo. The photos are not mine, so I have no control over the size/quality. Ideally I'm aiming to go to around 30cm x 30cm. One image I have is 1200x1200px. Will this look OK? Also, what's the ratio I should be aiming for so that if I get another image I can calculate its maximum size on a canvas while still looking OK? This is just for display in my house. Doesn't have to be art gallery quality. Just on the upper end of "good enough" will be fine for me. I'll be using the cheapest service I can get away with so I don't expect them to do much fancy reszing work or processing to maximise quality. Cheers.