To get an even white background, you have to use a backdrop:
Cover the ground and the sky with a white object that emits a white light [[font=courier new]mtl: illum=0 [/font] ](check my project file).
Here is what it will look like in sunshine:
and here is what it will look like with sky lighting (IBL) enabled :
And here is my project file:
Demo-backdrop.sh3d
Check out my settings, and you (or anyone) are welcome to use my white backdrop as you please.
Hope this helps.
Cecilia