The darker tones are too bright for what this is. You have a room with limited light that turns the walls to a washed out pink when they really should be a deep purple. Try taking a screenshot of your stage elements and overlaying copies of it on a layer above it while applying the 'multiply' blend in your properties to see what I mean. I took a screenshot and did the same and the pinks punch out more vibrantly due to the darker tones of the environment, but it also plays more to the dark, dingy room and cityscape outside the window. It also allows the radiant glow of the buildings to stand out more as the structures themselves are not only darker but so is the night sky. Here's a screenshot of when I did it.
https://www.newgrounds.com/dump/draw/c5dd177ec0648a223ef3676aa13e9f2f
My only other real criticism is that your background buildings are all copy and pastes of two buildings. This is not in itself a bad thing with the exception of a lack of variety but the buildings themselves are unimpressive considering the windows are just yellow dotted lines that don't all follow the same trajectory.
I would recommend you try using thinner outlines for when you're animating and then increase the line strength back to where you want them. I use the hairline stroke style whenever working on an animation because it allows me to use razor thin margins whenever I'm filling in gaps between frames, and it allows me to go as thin as 00.05 pixels. I mentioned this because it seems like your animation is being limited by the bulky outline strength you're using. It'll also help you develop outlines with seamless curves because you'll be better able to spot it when two lines veer off in different trajectories at their anchor points.
I admit I don't know what animation software you're using but Flash can go up to 1440p in the stage's dimensions, which also creates significantly more breathing room for getting sharper margins and adding more details. I mentioned this since the room feels stuffy but also sparse. I also noticed that the edge of the bed marks the vertical plane for your one point perspective.
Speaking of one point perspective, I noticed that the perspective of the room isn't perfect either, as the headboard of the bed veers off from the bookshelf above it the closer they both approach the vanishing point. In fact, none of the lines on the bookshelf itself follow the same trajectory, either. I would recommend creating a perspective grid that you could use with each new background that you draft. A perspective grid consists of a circle that encases the stage with lines meeting the inner edges of the circle starting out from the vanishing point dead center of the stage. Doing this will ensure that all of the lines in your background will always follow the same trajectory in your one point perspective.
Here's an example of a prototype I created of a perspective grid back in 2018, just to give an idea:
https://www.newgrounds.com/art/view/psychopath/perspective-grid-prototype-flawed