To create it, I have used blender, an open source 3d modeling program.
The instructions are quite simple (pictures help) and I hope you enjoy them
Here is the .blend file (you can modify it if you want)
Here is what the final product looks like: (more images on the last slide)
Step 1: The Image
In gimp (an open source photo editing software), I changed the text from
You shall not pass! ---- to ----- You shall not pay!
You can do this in pretty much any photo editing program