The team at my first tech job did this; I left my computer unlocked and stepped away, came back to find "I" had sent a joking message to the team saying that I

The team at my first tech job did this; I left my computer unlocked and stepped away, came back to find "I" had sent a joking message to the team saying that I forgot to lock my computer. It definitely trained that habit into me, I lock my desktop when stepping away even at home. I think it's probably a good technique, though it needs to be done with a bit of care to not seem too hostile or humiliating. Changing the desktop background seems like a good idea, since it's harmless, obvious to the user, easily fixed, and doesn't impede actual work.