One of the reasons it looks very washed out is also your lighting, it looks over exposed with no shadows to speak of. Lighting does a lot about the mood and getting the right look, the screenshots that Di$array posted shows the difference as well, so putting in a skylight and a directional light to simulate the sun, and…
+1 to Di$array there, its looking good, add add some colour variation. on your outside try doing something to the background instead of it just going into nothing on a flat ground. maybe create some trees or some type of foliage for the outside part. I dont know if its the angle of the camera but it looks like there are…