This Spanish Galleon took me about one and a half years to figure out the processes necessary for making a 3D bass relief of this type. Notice the edges in the close up images are not stair stepped like you see in most 3D bas reliefs with hard edges. To the best of my knowledge, there are no 3D bas reliefs as of yet of this type that have this high fidelity edge style.
This 3D bas relief looks good as a low or high relief.
The format of this file is in STL, however, it is not a watertight STL as the back is open, so if you would like to use it with rapid prototyping software that requires a watertight file you'll have to close it yourself.