Labyrinth Zone blocks
Take a look. as you see there are two blocks that you can see here alot throughout the level. One is a bird head and the other...um...is a wierd face (maybe another bird head)looking up with it's mouth open. You can see these kind of designs on blocks in later levels that are kinda based on the original Labyrinth Zone blocks. Like the pic below in Hydrocity.
I guess you can call the design on the blocks "a leaf-like cutout" but look at how it compares to the 1st bird head block (not the one looking up). Interesting, no?