I'm sure there are probably Hidden Mickeys, because they're all over, but the easiest way to find at least some is always to ask a CM who works there (usually not custodial). And every restaurant should have a fairly elaborate story behind it.
I know Sunshine Seasons is themed after the seasons, there are four seating sections, one for each.
Jiko has a whole story, the walls are the sunset, the birds fly into the sunset because in Africa that's a sign of prosperity, and the columns with hoops represent the hoops women wear around their neck--the more hoops, the more prosperous.
All of Liberty Square and Frontierland is themed geographically in order from Northeast to Southwest (where LS meets Fantasyland is Maine, Hall of Presidents is Philadelphia, the riverboat is Missouri, Big Thunder Mountain is Utah, etc.; Splash doesn't fit in though) and the interior of Columbia Harbour House is in three sections that represent three parts of the East Coast.
