Just wanted to share my experience with creating this amazing painting using the laser engraver machine. So basically what I did, is that I took classic painting canvas you can buy in many hobby stores, and took black acrylic paint, and painted it whole.
I would discourage you from putting thick layer of the paint, as it will then take many more passes to reach the canvas.
It took me really a lot of time to get the correct setting to burn trough the paint without damaging the canvas, making it yellowish and leaving it nice, clean and white.
I would suggest that you have at least one canvas for testing and to experiment with.
First thing you need to do is to focus your laser the best you can. I was using the 5.5W diode laser. I reached the best output at 2000 mm/min speed and 25% power. To get to the clean canvas it took about 5 to 8 passes. Depending on the paint thickness. On the thicker layer it took up to 20 passes. Also, I noticed that the speed does not affect the result, so I am using 8000 mm/min speed and 100% power right now.
Here is an example of one of my tries. This is 20cm x 20cm canvas, which took about 4 hours to burn out. Not perfectly clean through. There is still a gap for improvement.
This experiment looks much more cleaner and white, as I used white spray as base layer under the acrylic paint. Sadly there was huge problem after burning the paint out, as the spray paint was also probably little bit damaged in the process, and after touching the white places it smudget out to the painting.