Thanks all, but I had to do some more work on the scene after I tried to get my big stereoscopic 3D version.
The scale of the oak and the robots didnot fit at all so I played around for a while.
Also I needed many trys until I found a position of the oak in the left front where you don't see too many rectangular branches or flat leaves.
Now the scene is final and will be rnedered (in 1280x720 of course) like this (frame 1):
[attach=1]
and the 3d anaglyphic version for red-blue glasses:
[attach=2]