Decorating a level is almost as important as making it. Without it, levels seem dull and lifeless. Decorating includes decorations, stickers, background scenery, scene objects and moving scene objects. They may sound easy, but pulling them together is pretty hard.
Decorations, are, in it's name, almost only for 3-D decorating. They have no interaction with the player and objects, but are highly useful.
They are basically the two below descriptions, but not in the players path. They appear away from him or her.
These are objects placed solely for appearance, such as an apple in a place with an apple tree. They may be blocking off an area, but are much better compared to a basic material.
Moving Scene Objects
These are controlled by pistions, chains, motor bolts, wobble bolts, etc. They are more complex and may be harder to get the motion you want.