can anyone share some sample output?

I have a client that wants proof that we can actually output print-quality files as the output from the custom designs...

Can someone send me a few examples?

The goal is to use this for puzzles and small posters (with photos) in US LETTER size (or up to 9x12 inches).

How SMALL of a photo & what resolution should we REQUIRE for customers to upload them to get a great quality output?

Thanks for your help!