What a nice looking tileset!
Just a note on file formats. Illustrator can export plain text SVG files. If you included the SVG versions, people could use Inkscape, Corel Draw, Method draw, SVG-edit, and Illustrator to scale or edit them.
Inkscape is free, and is widely used by a lot of indie developers. Inkscape can import ".ai" and ".ai.svg", but not every free SVG editor can.