Update docs

docs/SCNGame/tilemaps/Map Object Classes.md

@@ -2,7 +2,11 @@ There are a variety of map object classes available to use when editing a tile m
 
 Objects can also be added to individual tiles using Tiled's collision editor. This can allow for sprite objects to hold additional collision information, as well as tiles themselves of course.
 ## Decor
-A semantic (no properties) type that specifies a TextureMapObject is to be added to the scene as a sprite.
+A decor or sprite element (that is, some TextureMapObject you wish to be inserted into the scene as a sprite) can be defined by inserting a TextureMapObject and leaving its class blank. 
+
+If the tile used for the texture map object has other objects attached to them, as done with Tiled's collision editor, those will also be parsed and added.
+
+TextureMapObjects may be used for other types of map object (e.g. when you want some image as a placeholder representation of some object, such as entities), in which case the class won't be left blank.
 ## Wall
 These represent basic walls that the player or other entities can potentially collide with. 
 **Object Type:** Rectangle