Great job for your first game! Entering a game jam right out of the gate is a real challenge and props to you for giving it a shot. One tip that I could give with any project like this is to stick to a pixel scale. Having objects of different scales, where one object has pixels that are larger or smaller than another, can really stand out and break cohesion in the world. Same goes for sprites that are anti-aliased mixed with hard pixel art.
Good luck on your future projects!