Uninstalling OS Lion, and transferring photos to MacBook if full restore needed
Use Time Machine to backup your entire system to your WD drive.

Once finished, clean restore your machine back to Snow Leopard, re-install your applications and then perform a manual drag-and-drop restore from your Time Machine drive back to your clean machine.

This will avoid restoring any upgraded system files, preferences or other content Lion would have upgraded at point of upgrade.

I've recently had to perform the steps above for a family member after a misbehaving Lion upgrade (bad kernel extensions or preferences causing random shutdowns).