The medallions in OZ:

 

The house in the top left corner with the tornado that brought Dorothy to OZ  is related to the movie therfore the motifs are black and white.

The grey hat surrounded with light golden motifs  represents the scarecrow

The red Balloon with the “State Fair” sign is in reference to the first book that I consulted to make this tale. It was Red Balloon Books and I LOVE that edition so I wanted to represent it.

The half of the head in the top right corner is the lion character.

The flying monkey on the left is one of the wicked witch's flying monkeys.

The crows are the wicked witch's King Crow and crows.

The apple tree next to the crows is the magical apple tree

The bucket of water in the center is from the witch who has buckets of water in her castle so that the winkies could extinguish fires if they arose.

The funnel hat represents the tin man.

The rainbow is also related to the movies and one of my favorite songs of all time. 

The red flowers next to the yellow (which is the yellow brick road) are poppies which the wicked witch had used a dark spell on to secretly enchant them to try to stop Dorothy and take the magic slippers. 

The munchkins are on the right. 

The medallion with a crown and a scepter represents Glinda the good witch of the South.

Toto is a reference to the movie as well and he is following Dorothy out.

The black dress and green leg on the left is Elphaba the wicked witch of the west.

The blue dress, basket, and red shoe, are Dorothy. The red shoe is in reference to the movie, in the books the magic Slippers were silver!

And lastly, the Basket is also a reference to the movie. The basket was added after the final changes in the production.