Nice to see someone discover this! I've always been partial to spot the differences and crossview images - I am able to cross each eye independently of one another, which makes overlapping these sorts of images very easy. For example, I could cross my right eye, while my left stays perfectly still. This causes instant double vision, and relaxing how crossed the eye is lets me line the images up very quickly. It's fun to do in places with a repetitive wall texture, too - seeing something in real life while adding a faux 3D effect on top of it is kind of trippy. Probably my most useless skill, but a fun one regardless.