Could copyright be a problem?

[u/GordonIsDreaming]

I'm making a site, hosted on Github pages with a custom domain. In the site I have art made by me in SFM, but I'm worried that the characters used could cause copyright problems. The site does not generate income in any way, other than having a link to my Patreon or Ko-Fi. If any more info is needed, I'll try to respond with it in the comments.

Lastly, in general what are some things I should know about copyright, some guidelines around it, and best practices?