How to make this thing?
This cries out for 3D scanning or use of 'topographic\level based image to 3D conversion' by way of specialized software. David 3D will be the absolute least expensive option utilizing '3d scanning', and there are numerous software packages that may make something somewhat sensible out of that design.
Personally, for quality, you would get the best result by actually tracing the design with the CAD\3D drawing tools and modeling it out.. Of course, this wont get imperfections, which in a game or movie might be achieved via texture maps and bump maps and alpha maps and so on, but for 3D printing it must be 'in the model'.
Consider looking into Blender or zBrush for programs that can modify a [perfect' 3D model from a CAD or 3D design program