Our files throw off some online printing companies. The images from your gallery are high resolution compressed jpegs. They print beautifully up to a size 16x20 (we've tested this at several printing companies to be sure!). What happens is, many printing companies use a quick and dirty quality control system where they only look at the image size, rather than the resolution. You can feel free to ignore those warnings and print up to size 16x20 with no loss of quality.
The images from our galleries are the same ones we use for all our in-house marketing materials as well as our album orders and print great!
If you are needing specific images printed at a larger size, please connect them with the photography manager firstname.lastname@example.org and she can help you out!