[the size of the print e.g. 20x30]-[your first and last name]-[a number].jpg or .tif, An example would be:
20x30 John Smith 1.jpg
20x30 John Smith 2.jpg
20x30 John Smith 3.jpg
For multiple files on the same upload / order you can just add a sequential number at the end e.g. 1, 2, 3 etc. as above.
PLEASE DO NOT NAME YOUR FILES LIKE THIS:
DSC_34244.jpg etc
This is a problem especially if you have multiple files and different sizes with your order as it's impossible for us to know what file is for what size/product.