You mention that your art here is "open source" but don't give a specific license. Could you add a LICENSE file to your repo so we know what terms we're under to use these assets?
I'd recommend one of the Creative Commons licenses, in particular CC-BY.
In one of your very old post you said you wanted to make a tool to allow you to automatically generate characters rather than have a gimp file. Did you ever start on that?
If not I think that would be a great tool to have and something I could put together rather easily.
Is there anyway we can clean up the repo at bit, or change some filenames. Some of the files seem randomly placed like tank1.png in the main directory.