Note that the copyright and stuff alike is from the author of the real skull.

I've just taken the skull and done some editing. I could spend some more time, but I just wanted some sprites to have something to move in the screen.

https://opengameart.org/content/a-load-of-overworld-34-rpg-sprites

This is the author of the skull I've taken. If you happen to use one of my edits, you should credit this author instead of me.

Stephen Challener (Redshrike)

He asks for a link on his profile together with the credits.

I don't really care about random credits and the effort I've spent is minimal, but be sure to credit that guy and put his link on whatever you happen to use it.

It should be easy to recolor one version if you happen to like one of those.

I'll also leave the xfc gimp file if you happen to use gimp.

I'd like to publish as public domain stuff, but it's an edit from an existing work, so I can't.

I'll suppose it counts as if the guy made those versions too :D