A recommendation for everybody who needs passport photos:
We had to renew our daughter's passport. We got her passport photos taken at Walgreens. At the post office we were told that the US State Department may reject her picture since the background is rather pink than white, so we had her pictures retaken at the post office. Of course that doesn't mean that all Walgreens passport photos will have a pink background, but it was only $2 more at the post office and you can be sure that the photos are in compliance with government regulations, so I'd recommend taking passport photos at the post office.