Some of these look good, but you got some minor problems-
-Some of them dont have delta and it makes it look like one big static layer.
-Using the jigsaw method is great but not when you want to have some depth.
-In madness city, the floor doesnt match well.
-also, your moonlight stage-
i happened to find a stage that looked very similar to it....
The other stage-
It looks like all you did was change the background and add your own sprite, all you changed was the back layer, everything else is the same.
I dont have nothing against you, but you could have tried to change more things. It looks good nonetheless