I'm probably the last person in the world to know this, but the Disney Imagineers hid Mickey Mouse images, shadows, outlines, etc. all over Walt Disney World (WDW). Apparently, when Epcot was being built, there was a controversy over whether Mickey would be reserved for the Magic Kingdom exclusively or if he would show up in other places. So, some rebels decided to start hiding Mickeys in Epcot and the other parks.

These can be in many forms. I only found a few including the shadow above in a mural in Animal Kingdom. More often, I found the three circles that signifiy his head; for instance, along the bottom edge of the bells hanging from the pagoda in the Japan pavilion at Epcot, the decorative cutouts were Mickeys.

Anyway, it was fun to search for them as I walked through the parks. Maybe you'll have better luck finding them than I did.

Here are a few guides if you want a leg up:
HiddenMickeys.org Hidden Mickeys (the book) WDWInfo