Etsy has a ton of 3D laser engrave files available for purchase. This specific one I purchased from LaserSpot on Etsy. I am unable to share the file though. 

Go to Imag-R on the web. It is a free image editor that works great at fixing pictures for laser engraving. You will have to use your judgement a bit on how to properly fix the picture according to the wood or material you are using. In this case for the wood cutting board all I did was upload the picture. I resized it to the 12x12 inches that the cutting board was going to be. I used 318 DPI. I then set the material to Kasia Grayscale. Then I sharpened the image to 50%. Then go to Gamma Adjustment and lighten it a bit so that the dark areas are not so black. I cant give an exact amount of how I adjusted it but just do it so its lighter in the shadowed areas. Then go to contrast and equal out the colors just a little bit. Its a bit of trial and error here depending on the material you are using. Once you are happy with the image download it. 

Download your image that you saved from Imag-r and sharpen it a little within XCS. Put your board into the xtool machine and make sure it is aligned. The measure the depth. Then mark your parameters for the cutting board or material you are using. Then for my settings I did 40% power, 200 speed, 200 lines per cm, 1 pass and do it in Grayscale mode. It took about 2.5 hours to do this board at these settings. 

Once the board has been completed, let it rest for about 5 minutes. Then take a microfiber cloth and the 70% isopropyl alcohol and put some on the cloth. Then wipe the board down with the cloth to get any smoke marks and residue off. A couple passes will do. Let that dry for a couple minutes. Then take the Howard's food grade wax and a microfiber cloth or waxing cloth and wax the board down and let it dry overnight. You are done :) Good luck. I am brand new at laser engraving so if I can do this so can you :)