I like how it looks like a traditional style Mario game. I'm honestly not sure what to recommend or say about it, it looks pretty good, except perhaps the pipes and piranha plants clash with the rest of the level in the third screenshot a bit.
You might wanna add some BGOs to the cave and the castle, they still look a little empty as they are. Other than that, I can't give you much in terms of feedback.
Also you might want to add a few more coins here and there. I don't know if that's a thing all throughout the level or not but that's just from what I can see.