You can follow hashtags such as #photography or whatever you're interested in. Posts with those tags will appear in your feed.
There's also a group account you can follow at @photography which will share photos posted to it to all the group's members.
Also, don't want to overwhelm you, but there is an entire photo sharing social network on here called Pixelfed. It is compatible with Mastodon, you can follow Pixelfed accounts from Mastodon and vice versa.