Personally I think you should re-work the palletes. If you're going fully with a dark setting, you should recolor the sprites and the blocks too. If you wanna keep it as vanilla as possible, just reduce a fixed amount of saturation for every color, like 20 or 30. I do think the bg palletes are bad overall, so you should consider working on it a little.
Aside from that I don't have any complaints. It's a very simple and fun looking level. I do question your choice for terrain design though, like in this screenshot:
I know that you replaced the cutoff tiles, but it still looks very weird. I feel like you went with a very complex tile mixing when you could of just make it simple. Fancy tile cuts and mixes generally makes for a good aesthetic, but it has to be in the right place.
I could suggest you do make it like this // or if you wanna keep the concept
These are just suggestions though. I did like what you brought in the vid and I think it's a good level, just give it some love and it'll be great.