you might wanna be carefull with a too dark background since it will automatically make people create darker artwork since it will look brighter with a dark hud. just a heads up, maybe it wont even matter.
I dont know it anyone said this, but it would be awesome if there could be an instance funcion. where you could have one tile, like a terrain tile for example, and have that be instanced several times, and as you changed one, you'd automatically change the others.
Kaz