Some other photos:

Some photos from the conference:
1. Ton Roosendaal is going to make a speech

2. Sergey Sharybin

3. Blend4Web and Blender together
from left to right: Misha, Yuri, Ton, Alex, Evgeny
4. Dam Square

5. Ton opens a present from Blend4Web

If you want consistent behaviour across different systems keep aspect ratio constant. As in your example it would be 1920:1080 or 16:9. For particles i'd recommend using textured particles instead of HALO ones, because the maximum size of HALO particles constrained by used hardware (check your Aliased Point Size Range here).