I’m not sure whether this is just me but I’d like to be able to edit the covers for my playlists in the same way I can edit covers for regular albums. It’s a little thing but it would really make my playlists look a lot classier than just the tiled four covers that you get as standard.
A lot of my playlists are of songs I’ve heard particular radio DJs play, so it would be great to have a picture of e.g. Giles Peterson as the cover for my Giles Peterson playlist.
I’ve merged your post into the Feedback > Feature Suggestions topic, if you’re interested consider voting for it via the vote icon at the top of the topic.
Make the ability to change the playlist icon when you click on a playlist and see the icon/photo in the top left and it is a bundle of the four songs that are first in the playlist and instead of being forced into seeing that instead allow users to change the photo/icon to a photo of their desire for that playlist.