Alright. Still here. Planning, listing concepts, building a library of assets. Do you have a preferred tool for sharing data?
So level backdrops are currently single 24bit png format images, dimensions don't have to be POT or anything, so for example the largest level is probably ROOSA, which is 1267 x 1087, and the smallest is Wasteland at 576 x 464.
From these I then use sprite illuminator to generate a fake normal map for lighting, though if you really want to get into that stuff (or if you use 3D assets that you then bake down to 2D) you can paint/generate your own normal map data if you want to make it look a bit nicer.
You can also build much bigger levels if you want to - I can use a simple script to split the image into small chunks for rendering so you don't need to worry about that.
Dropbox is fine for us at the moment for sharing, I have everything backed up to a private SVN which potentially I can give access to in the future but for now dropboxing stuff to me would work fine!