So, the issue with Mastodon is that there's no global search and discovery. In order to be found, things have to be hashtagged. The problem with hashtagging is that twitter clout weirdos made hashtagging SO uncool that nobody, anywhere, wants to do it anymore. So, do search hashtags related to your interests and follow folks that are posting to them, but that may not get you too many hits.

If you're on an instance that isn't enormous, try the local timeline to identify some folks to follow. On big instances, that's not usually useful because it's too big a firehose.

For art specifically maybe see the stuff that curator on mastodon.art boosts: https://mastodon.art/@Curator

This is why Lemmy/Kbin is potentially cooler for some applications than Mastodon. Since communities are (a) not stigmitized like tags and (b) also mandatory, plus search exists, it's much easier to find things! (Although there's not yet much to be found)