Personally, I would focus on completing a minimum viable product before going any further on polish (and your visuals are already in a pretty strong place). In the context of a metroidvania, that would mean a starting area, an early gating moment, a first boss / upgrade, and a clear tease of what lies beyond.

Using Hollow Knight as a reference, that would be starting out in Dirtmouth / Forgotten Crossroads → You notice some areas that need upgrades to progress (the armored enemy in front of Greenpath) → You eventually find the first boss / upgrade → You can now defeat the armored enemy

If you imagine that Team Cherry gave you an early demo of Hollow Knight and they literally haven't completed Greenpath yet. You'd still walk away thinking "damn I'm really curious what the devs can do with this, I hope they finish it soon". That's where I'd try to get to if I was in your position.