Listen, dude. I'm 40 and I have been around the block a few times. My best advice to you, is to give yourself the ultimate Christmas present and resign tomorrow afternoon. Having gone from drone, to manager to executive, I can tell you this situation is not going to get any better. Your boss LIED about you in your employment record. Words like violent, harassment, insubordination will stick out like a red flag and the circumstances will never be investigated by anyone looking at you for an internal move. What exactly is "violent" about a dinosaur in a F-15? Does he think you are making a subtle threat to bring the real thing to work? If you want to take it further, have your letter ready with a copy of the image, go to HR and ask them exactly what about it is "violent". If they can't give you a good answer, tell them you want to file a complaint of harassment against your boss, since it is not "violent", and he lied on your employment record. If they start to be all, "It's inappropriate for the workplace etc", ask them where the desktop image standards are written down, and that you want to see exactly where there is a prohibition on dinosaur pilots. If it looks like it is going your way and HR is on your side, you are safe. Your boss can never touch you, because he, too lives in fear of HR. If they are siding with your boss, insist on making the formal harassment complaint, then hand them the resignation letter. Merry Christmas!