During the last few days on working on this project I put all my assets inside UE4 scene and then tweak around a lot to make it look good.
When I started this project I had some base narrative for this environment in mind, but after working on it I decided to focus more on just making this environment believable, like a place that somebody could live in. This is part of environmental storytelling to.
Until I put everything in the one scene I didn't really know how all elements will sit together. Even when they look good on they own they might look bad together, and that what's happen here. ( and I supposed that's why making concept art is a good idea)
Take 2. Unifying colours, making everything sit together nicely.
Take 3.
Adding them details.
Take 4.
Playing with lighting and postproces volume. Adding lighshaft Some changes in room shape.
Optimization.
In UE4 you can check how performance heavy are some of the elements of your scene. Like polycount and shaders.

(it just looks nice in on;y lighting mode)