Repro steps:

1. Open provided project
2. Click on "File" -> "Build Settings" -> "Build"
3. Create a shortcut of the just built .exe file
4. Right click on the shortcut and press "Properties"
5. In the "Target" field, after all the text, write "-batchmode"
6. Press "OK"
7. Start the build with the shortcut (A folder should appear called "UnityHeadlessRenderingScreenshots" where 20 screenshots should appear over 20 seconds, showing whats happening inside the game)
8. Enter that folder and see that all the screenshots are the same

Expected result: The screenshots should look different as time has passed in the build
Actual result: The screenshots all look the same even though time has passed in the build

Reproduced with: 5.6.0b3, 5.6.0b5, 5.6.0b11, 5.6.0f1, 5.6.0f3, 5.6.1p1, 2017.1.0b6, 2017.2.0a1
Regression first introduced in: Version 5.6.0b3 (358ff4ed3952)
Did not reproduce on(All screenshots are grey): 5.5.3p4, 5.6.0a1, 5.6.0b1, 5.6.0b2

Note:
There is a particle system in the project and because of it,you should clearly see that the screenshots have changed.
This affects only the particle systems and UI components
Normal mesh based GameObjects will rendered as expected