Turn any photo into a dot grid artwork with these Photoshop actions. You'll get great results with dots that change size. They get larger in brighter areas and smaller in darker areas. Free download available.
Open up a new file 2248 x 3400 px in 300 dpi. Make a new group called "Background", give it a color and copy the desert scenery stock inside and put it at the bottom of your workspace on a new layer called "desert".