Wow, magnificent set of images. Every single one exhibit great attention to every detail and all are equaly interesting and convincing. It is difficult to point out any specific aspcet, light, materials, details, decoration... Maybe, just maybe I would put spot on the shaders, but more as integral part of the overall effect. Like the wall shader on 2nd image that play along with highlight from the lamp... Can you tell a bit about light you used? Is it hdri or corona sun/sky... I love how clean the shadows of soft/diffuse daylight appear, not sure if there is some secret, but could be... Do you use portals in openings?