DeviantArt user Kaiseto, aka Kevin Chaloux, offers up some fantastic pixel art. A few years back he made the effort of converting most of them to Creative Commons.
What does this mean? It means you can use the art for yourself providing you do not make any money off it. For example, you could use it in a Roll20 session or as an avatar in Discord. You can’t sell it or attach it to media that you charge people to access like a Patreon but you could use it as icons in your free to view Twitch channel.
If you use this art; you have to credit Kevin Chaloux as the artist. You can’t pretend you did it.
At the time he put together this long list of pixel creations you could access. It’s well worth checking out. Here’s some samples;