When you are attempting to print pictures, you may see a warning icon next to some of them and a message may display, stating, "Warning: One or more pictures are lower than the recommended resolution. Click this icon inside the preview to remove the image."
This message indicates that due to the low image quality, a printed copy may not live up to your expectations. If you would like to remove the image from the print job, simply click the warning icon in the upper left of the image.