I regularly sell 20x16 & 20x24 prints from a 35mm neg, both colour and black and white. When it's matted and framed, the first thing people do is hang it and step back. It's very important to think about the final viewing distance. Admitedly I scan all my negs and send them off to print at this size, I only offer 8x10 or 12x16 hand prints because I find bigger to be a pain in the ass.