I used to do the same thing, but a little differently. I used SleepWatcher as well, (
http://www.bernhard-baehr.de/ ), but set it up to run the following script, which uses isightcapture (
http://www.intergalactic.de/pages/iSight.html ) to do it all in the background:
NOWDATE=`/bin/date +%Y.%m.%d-%H.%M.%S`
/usr/local/sbin/isightcapture ~/login_images/$NOWDATE.png
/usr/bin/scp -o ConnectTimeout=5 ~/login_images/$NOWDATE.png me@myserver.com:~/login_images
Where I have an SSH fingerprint for me@myserver.com installed. This let me back up the images to a server, for convenience and security.
Edited for code formatting.