The GNU Image Manipulation Program (GIMP) is raster graphics software that can be used to design and manipulate raster images. Raster images can be etched using the laser cutter, or can be used to It can also be used to create sketches that can be imported into 3d design software.
The fact that GIMP is open source software means that there are many user designed plug-ins available, and it is even possible to write simple programs to automate many processes involved in creating designs.
GIMP is open source software, anyone can download and install it for free on their personal computer.
Install Link: http://www.gimp.org/downloads/
Tutorials and information can be found at http://www.gimp.org/docs/.