Having a transparent layer will make your color count rocket, since the computer is basically addin virtually unlimited amount of colors with its transparency calculations. It doesn't care about your palette or combining colors.
I highlighted 10 % of your least used colors: i.imgur.com/LDrLPcy.png. That's ~25 colors used by less than 0.1 % of the pixels in the piece. All the purple pixels were once some other color, and taking a quick look you have very similar colors in your palette which could have been used instead. Having control over your palette (through color conservation, among other things) is a key skill in pixel art.
Thank you for feedback!
How can I manage to use less colors here? Yes, shadows are transparent layer.
Looks great. You should add some details to break up the monotony of the books. Like some shelves with figures etc on them.
awesome job on the spiral staircase and really like the table textures
Lovely! Would be awesome if the shadows swayed as the fire flickers. Still though - Nice!
For minor feedback, the black outlines on the books come off maybe a bit too strong, the candelabra isn't casting light, the highlights on the staircase make it a bit hard to read, and the color count is really high (255; I imagine the shadows are a transparent layer?) - but overall, I like the atmosphere. I'm thinking of a point-and-click murder mystery adventure game.
Almost brilliant. Except stairs.