The environment for this game really set a tone. The donut shaped rocks out in the distance along with the creeping fog and dreary red sky. I think you did a really awesome job!
I am not sure if you are aware, but Godot's audiostreamplayer have a built in randomizer setting in which after selecting you can choose the range of pitch frequency and different streams to play each time that sound effect is called. It might have been a good effect to use for the pick-up sound to add a little more variety.