What use rules for your asset? You can read a bit about licenses here https://creativecommons.org/about/cclicenses/
Viewing post in FroggyPixel's Basic Tile Asset comments
1. You have already used png format but rename file now :)
2. If you think that it was useful for you, you can leave a comment here to support my proposal about making metadata more visible for those who are interested in it https://itch.io/t/2919128/metadata-encouragement#post-7952450