Simple motion videos
Steven Williams
Even a larger selection of video render types of the cover art would be nice. For example, I like the old cover art style before it was changed. (which I suspect it was done to reduce rendering time.)
Gainn
The lyric video playing instead of just a static image would probably be a nice visual improvement.
J T Brown
And removing the Udio mark would be a nice option for subscribers. This is pretty common on content generation platforms: "Remove Watermark" is a link that leads to a subscription page.