for sure, i would love to contribute some tiles for something like this
the reason i think it would be cool for it to not be too restrictive in terms of quality and style is i think part of collective effort like this is that it can go beyond the mainstream notion of “quality” and “how good something is” and be more about the freedom of creating something and performing things together
so if you are too restrictive and say “this is ok, this is not ok” people might loose the enjoyment of it. but by using the same tile size and palette the tiles will in some ways match, and i think that would make a really interesting tileset
with that people could make games that are focused more on having diverse content, and not just pretty tiles