Your lighting is decent- but the chair seems to float due to its shape, reflection, and shadow casting: the problem being the reflection/shadow don’t show up and leave the ball disconnected from the floor. Composition wise- I would suggest that you either reconsider using the chair at all, place it more interestingly to the scene, or decorate the scene with other objects. The chair castes no reflection, little shadow, and no caustics. Since your goal is lighting- which in turn includes rendering- I think you need to ground the chair in the room by showing off in the render how everything is related. Having some green color spill thru caustics or global illum might help- or even cheat it with an extra green light. Definitely having the chair show up in the reflective floor will help with connecting it to the ground. Though this work is not about modeling- I do think some supports for the chair are in order- how can I sit in it without it rolling away? Adding some bump and random spec values to the tiles might help them to appear more dimensional (or is that wall paper? It looks like the color of tiles but paper thin). There also appears a strange boxing artifact on the camera left wall- maybe caused by compression.
There are some nice things happening in this image- I like that corner of light you got going. Color scheme is appealling- and the lighting feel accurate to daylight.
Good work and good luck