To make gcode files that are compatible with this cnc machine you have to use the Inkscape.

Inkscape is professional quality vector graphics software which runs on Windows, Mac OS X and Linux. It is used by design professionals and hobbyists worldwide, for creating a wide variety of graphics such as illustrations, icons, logos, diagrams, maps and web graphics. Inkscape uses the W3C open standard SVG (Scalable Vector Graphics) as its native format, and is free and open-source software.

Download and install Inkscape from here (Important: download 0.48.5 version)

Now you need to install an Add-on that enables the export images to gcode files. This add on can be found here with installation notes.

Setup Inkscape for first use

Open the Inkscape, go to File menu and click "Document Properties". See the 1st image above and make the changes, make sure to change first to "cm". Now close this window.

We will use the area within 4 to 8 cm. See the 2nd image above.

How to print texts

Put text, change font to Times New Roman and size to 22. Now click on cursor icon and center the text like the 3rd image above. Select Path from menu and "Object to Path".

How to print images

This is more difficult than texts. Images must have a transparent background. Drag and drop the arduino logo image (download it from files) in Inkscape. Click ok to the next window. Now you have to re-size the image to fit our printing area, see the 4th image above. Click Path from menu and "Trace Bitmap".

Make changes as the 5th image above. Click ok and close the window. Now, move the gray scale image, and delete the color one behind it. Move the grey image to the correct place again and click from Path menu "Object to path". The 6th image above show how to delete image outline.

Export as gcode

Final, go to file menu, click save as and select .gcode. Click ok on next window. That's it! Ready to go! Use the gctrl.pde app to print the gcode file on your new Arduino CNC Plotter!

I will make a video on next days about this procedure because it's little complicated. It took me a lot of time to understand how it's working...