A true "custom printer" will print any size and aspect ratio you want. I use Coupralux in Dallas. They will print my full image, without cropping, with exactly the border that I request. They will print a "full-size" image, with exactly one printer dot per image pixel, or any size larger or smaller than that.

Coupralux will also spend as much as 30 minutes (some techs will spend up to an hour) doing final adjustments to make sure their process gives the results that I intended with no extra charge. I've not printed there in the last few months while recovering from knee surgery, but my cost has always been reasonable...$.10 per square inch of printed area and $.05 per square inch of white border. This is on Baryta paper, which is very nice, substantially heavy, textured material.

I'm sure other printers offer similar service and prices.

I'm doing a presentation for junior high children on Composition, and want to start with the question, " what the difference between a picture vs a photograph?" My answer is a picture is a memory you take for memories sake, a photograph is a memory you take after planning it out and carefully choosing how, when , why , where and who.
I know you hogs probably can give me a better description and that sometimes a picture becomes a lucky photograph. Any positive help would be appreciated.
Thanks.