Not all photos are going to engrave well. Photos that laser best are photos that contain a wide range of light to dark shades and everything in between. Photos with large areas of a single color typically do not engrave well… especially when working with wood.
Most photos look better if they are engraved at lower resolutions than standard engraving projects. Resolutions of 200, 300 or 400 DPI are standard for photo engraving with 300 DPI as the median being most commonly used.
When selecting a photo for engraving, below are several considerations to keep in mind: