Then perhaps you should use a different hdri with more details. Are you using a free or a commercial one? There are some quite high quality free maps on this site http://hdrmaps.com/freebies
Try using one of them, they give good looking results. It could also be something in the render settings, you should be able to increase hdri’s exposure in vray, somehow. You could also use vray’s physical sky model. I can’t help you with these though, I was planning to start learning vray these days for my current project, I have no experience with it. And on top of that my power supply decided to stop working last night or even fry my workstation I don’t know this yet. Avoid throwing lights in the room for sure, if you have to use lights make them the size of the windows and put them a few inches outside of them. Add some directional light too, sunlight will make the room look nicer and better lit. A parade as a background would look impressive, you can paint that in PS or go crazy and make it 3d. 
Sorry for the wall of text, once again.











