Oh by the way when bat hangs from roof the re-image looks like bug
Enemy ideas: (with minimal or re-useable sprites)
1. Spider (plain), which dangles from roof on string stationary, bump it and it hurts or you drop coins
2. Spider (with green spots), moves up and down on string, squirts green poison, little over time damages you and makes you drop bones, unless you kill it then you instantly cured.
3. Spider (with red spots), same as above plus it can crawl on wall to get closer to you. If he is too easy make his attack also slow Player.
4. Rat (eat it, you can stats), but if you dont and a spider eats it, then spider upgrades to a better spider.
5. Rat with red eye, same as above, but he also poops or farts poison gas!
See not that difficult.
Re-use and add integration and depth with variations on same concept.
I really think there should be enemy (at least 1) already from the start!
Good luck for JAM.