At a minimum, you should be sending images that are at least 499 x 499 pixels, this ensures that your print is clear. When you’re ordering through the app it will warn you if your pictures are smaller than they should be. If your image is too large, it simply won’t load. Most phone images will be perfectly ok for this printing, but keep in mind the dimensions of our Mixtiles - if you have taken a landscape or portrait image, it may not fit the way you envisioned on the final product. If you do run into any issues you should contact their customer support before committing to the purchase.