So I think that you're on the right track. I take it you don't have that much experience in game design since it is unfortunately unappealing. However at your level things I would recommend is:
1: The Background looks really bad so I would use the main menu's image as the background and make all the enemies, and characters sillouhettes with their eyes glowing.
2: Make the movement better and more natural such as in Binding of Isaac
3: Add physics It is probably the most essential part that is missing. Even if its only on the witches hair or cloak (and make it look good)
4: you need to keep increasing the difficulty. I thoroughly enjoyed the Frankenstein fight but after that it became easier and easier.
5. Last but not least.: this is more of a suggestion than a criticism. Make all the blast attacks shot from enemies knock against the walls of the room so that more skill is involved.
So that's it from me. I still enjoyed playing through the game and I would definitely play it if it gets reskinned and changed a little.
P.S. The rolling pumpkin looks fantastic!!