I follow your thread for a while, because very interesting, but unfortunately I think you are on a bit wrong path. I would not call it photo realistic, rather photo based, sorry. The scenes you published so far look not as a harmonious whole, but some separate sprite-like flat objects having nice photo skins, in front of a photo based sky cube. The final result is far from realism, everything "lives" separately.
Hopefully, as Unity5 utilizes PBR, something very similar as UE4, you would be able to move towards the right direction, a few examples: - create properly shaded vegetation leaves (taking into account both sides: lighting through leaves, subsurface scattering) - SpeedTree could help also in proper wind behaviour; - real reflective metal materials for helmets, - much better wooden and stone surfaces really reacting on player/camera and Sun directions and movements/rotations, to avoid the current flat effect, - real far view terrain with high quality dense, instanced vegetation, and forget the sky-cube background; - real living sky with realistic clouds and Sun; - realistic shadows taking into account the actual sky and environment lights.
Epic provided a little blog post about their photogrammetry methods, how they handled photos and converted them into textures, when made the Kite demo: https://www.unrealengine.com/blog/creating-assets-for-open-world-demo (you can get a lot of assets for free, but currently the demo assets make some crashes with UE4.7.5, it will be really compatible with the upcoming UE4.8)
Basically your biggest mistake is that your textures are "alive". They should have a flat boring look without lighting similarly to a level in WED, and should get alive only after setting the proper shaders and lighting.
I hope you do not take my opinion wrongly, I just try to help your work to go to the right direction, to have good results after a lot of efforts
