It's a lot easier to just generate a random private key using bitaddress or vanitygen and just save that in a text file. Then you zip or rar it and copy it to several places like in a floppy, usb flash drive, SD card and printed on paper, stored in an envelope, locked in your safe or vault.
If you really want to use a photo, take a picture of the sky, or someone said take a picture of complete darkness (cover the lens) while setting the ISO to maximum, to get noise from the CCD or sensor. Export the RAW file or the highest quality jpeg, depending on your camera model.
Best idea itt