detailing feedback per porkchop's request (including things she did not ask for feedback on)
the question i got was "how do i make this not look like a big box?" to which my response is, skyscrapers are just kinda big boxes, and there's not a lot you can do beyond altering the gameplay space somewhat. that said, i think it looking like a big box is fine - just add some articulation to the otherwise flat shape.
for example, you could make the verticals more pronounced, so there are vertical lines going the full height of the building with ribbons of windows between them:
you could also get the same effect by removing the horizontal bands.
you can also choose to do the exact opposite, and make the horizontal bands more pronounced. however, i think you'll find that most skyscrapers tend to make the verticals stronger for aesthetic reasons. adding horizontal bands also means introducing ledges that players might think they can stand on.
for bonus points, make this symmetrical! (doesn't need to be fully symmetrical across the whole building, i realize that would cause a lot of layout headaches. just give it a symmetrical design where the tower protrudes outwards.) the section of roof on the right could be made an "indoor-outdoor" space where the windows have been removed and there is a seamless transition to the fully outdoor roof. having outdoor sections behind the facade of a skyscraper is not unheard of.
noticing this shiny chrome metal in places where it doesn't feel like it belongs. consider a plain grey metal instead
there are some floors that this elevator doesn't serve? which isn't unheard of in skyscraper design but it does strike me as odd here. also typically elevators come in multiples so that you can wait in one spot and grab the first elevator that comes, but you'd need to make room for that sort of setup somewhere else.
nudge these floor tiles over a bit to line up with the geo
consider removing these lights so that the balcony above isn't lit as brightly as the rest of the gameplay space. the balconies on the left side of the image are very clearly not gameplay space because of how dark they are, but the lit balconies are ambiguous. the lighting overall is also pretty flat, but i'll stop here because i'm assuming that this lighting pass is preliminary and will get some more polish.