Image resolution refers to the sharpness and quality of an image. The higher the resolution, the better quality the final printed product.
We advise that all images in your artwork should be 300dpi, or 150dpi for banners and boards.
A note on imagery - please be sure that you have the right to use the image in your design for the purpose of your design. You’ll need the correct permissions from the photographer and possibly consent from people within the image or their parents if they are under 18. If you are choosing imagery from an online image library, simply check whether the picture is allowed for commercial use. Free sites such as unsplash.com have terms & conditions areas where you can fully understand the rules around commercial use of images.