Download and unzip the artwork.zip and in there you'll find the PNG files. These files are ready to print and I suggest Sticker Mule for high-quality, color correct, stickers.
The application used to create this artwork is Adobe Illustrator.
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Please contact me if you wish to use any of this artwork for commercial purposes (anywhere revenue is obtained, including advertising).