i'm not sure which release you are using, but if it is the istock one where they say to include a photo id... i don't bother adding an actual photo id.  I think most people aren't really that eager for me to photocopy their drivers license to send away on the internet.  I do however cut and paste a little picture of them that i paste onto the scanned model release (this also helps to remember who the release belongs to (if you have a hard time remembering their names)