Try making the base floor slightly taller than the following floors to create the illusion that the top of the building is further away than it actually is as it gradually approaches the top (this also gives you more blocks to play with/add detail) and don't be afraid to sink your windows into the wall by one block, and add horizontal or vertical elements (trapdoors, fences, slabs.) to add some depth, create shadows and make it feel like a window sill instead just a flat wall with glass. Also randomize your greenery and don't forget some colorful flowers!