It seems like a good start. The illustration definitely matches the genre, and I think the title font does, too. 🙂
1. Maybe make the title taller or space out a bit more, overlapping more of the stage? Possibly move up the series name so that it fills more space? It feels like there’s a lot of empty space under the author name.
2. If not changing the title to overlap the stage… this may sound silly, but I’d suggest having some sort of cute animal on the stage if there’s any in the story. It seems like a lot of cozy mysteries have a pet on the cover. So if there’s one in your story, maybe see if they could add that to the cover?
3. Maybe darken the shadowy person in the balcony area? I didn’t notice them until after looking at it several times.
Good luck with revisions. 🙂