Absolutely excellent work, and on subject matter which is always in demand.  Thanks for making it, and thanks for the generous licensing as well!

These are great, nice work

Much better than mine!  *silently fumes*

This is great. Surt, you are becoming the Paul Erdős of open source pixel art. Just more and more good tilesets to choose from. I hope you don't collapse from exhaustion anytime soon.

Nice work!

And that palette is really tempting me to make some pixel art.

This is perfect for a Drip remake I've been working on.

This screams for some valves and vents ;)

Made a game that uses these for a parallax background: http://github.com/buch415/marble