Lots of great artists are on Mastodon instances, like mastodon.art. Including their image posts means you can see some really good paintings.

It just depends on how you want to use your account. I can see wanting to follow PeerTube or Loops accounts from Pixelfed. I follow a few Mastodon users who just post photos.

The default behaviour is to only show content with attached media but you can change that in settings too. So you can use it as a microblogging service if you just like the look and feel of Pixelfed.

Edit: striking out the falseness

I'm not sure. I don't think I've ever seen a Lemmy post there, though I haven't spent a ton of time on that TL. It might be different because all Lemmy posts are posted to groups which aren't supported by Pixelfed yet. That's just a guess though.