This is an OpenSCAD script and a Blender-created STL that demonstrate methods for creating a "hand hammered" effect programmatically and via modelling.
You can read more, and watch a quick tutorial video for creating it with Blender, on my blog post: http://wp.me/p2hTaI-iY
Feel free to look at the code to see how to create the "hand hammered" effect via code. If you want to render and create a STL from within OpenSCAD, be aware it takes a really, really, really long time.
Note that the STL has its own support structures built in, and you do NOT need to print with additional supports or rafts. You will need to remove the support before inserting a screw into the screw hole, and the inside will still be a little messy.