Here's a Broken Tower for a 2D isometric game.  It's designed for a base tile size of 64x32 (e.g. the ladder hole in the middle is that size).

Also attached is the Blender file and the GIMP layered file.

The method I used to create layers:  I rendered the entire tower first.  Then used those blank planes to render just the foreground and just the above-ground.  In GIMP I start with the foreground layer, use "Alpha to Selection", shrink the selection 1 pixel and sharpen the selection, and delete that selection from the lower layers.  In a tile-based engine you'll want to slice up the layers in fixed width sections as needed.