At the exit of the Fantasyland Train Station, follow the path to the area in front of the entrance to Dumbo the Flying Elephant. Tracks of a large and a small elephant (Mrs. Jumbo and Dumbo) are imprinted in the cement. These elephant prints come together at times to form classic Hidden Mickeys. Here's a decent classic Mickey image near the entrance to the FastPass queue for Dumbo.
In the last scene of Walt Disney's Carousel of Progress, do you see a Hidden Mickey formed by the pans hanging in the kitchen? (Thanks to William Shelton).
Also in the last scene, a Hidden Mickey is (unfortunately) not reliably present on a posted note on the right wall bulletin board. I didn't see one during a recent visit.
Here's a good example of the difference between a Hidden Mickey and a decor Mickey (decorative, meaning not hidden). In Mickey's Star Trader's shop, classic Hidden Mickey holes are drilled in some of the metal support poles holding up merchandise racks. (These support poles with their Hidden Mickeys can be spotted in many Disney stores). The large classic Mickey shapes on top of the support pole and on the rear wall (at the left middle of the photo) are, in my opinion, decor images (not hidden). (Thanks to Justin Lewicki, and Alena White).
I stopped by Mickey's Meet 'n' Greet on Main Street, U.S.A. to check out the gift shop Hidden Mickeys: first, the classic Mickey locks on the metal merchandise display table that faces one of the exits from Mickey's dressing room.
And the classic Mickey-shaped front door of the birdhouse from the now-closed Mickey's Toontown Fair. The colorful birdhouse sits on a tall merchandise cabinet inside the gift shop.
I like Hidden Mickeys to stick around a while!