I bet your wall clock is not as cool as the Moire Seconds Optical Illusion Clock. This clock gives you the impression that the image on its face is changing as time goes by. How? The second hand of the clock is connected to a mask that rotates, gradually revealing different parts of the clock face as time passes. The illusion is based on moiré-effect.
Zoltan Kecskemeti B. has posted more photos and info about this clock on his Behance page. What do you think? Are you impressed?