I'm totally confused now. Making a Web CS2D Map Editor is an awesome idea, but uploading additional sprites, sounds and other stuff would be hard. Also making In-Game CS2D Map Editor would be also cool and much easier to collaborate with others, and everything related to map is already uploaded at the map.
@ DC: I bet that it's impossible to hide sprites and objects like trees in-game. How to hide them? Maybe Trigger_Start does that but idk...