I was looking at some SS at diablo3.com and I was caught by a significant variation on
the illumination of a specific place.
The first SS was a witch doctor’s SS#101 released several months ago.
http://us.blizzard.com/diablo3/media/screenshots.xml#101
I particularly like this SS, but look again…
Demon Hunter’s SS#151:
http://us.blizzard.com/diablo3/media/screenshots.xml#151

If you compare them, they seem to be the exact same place. Look the rocks shape, the
dead body and even the beasts. There are some changes as the rock sculpture (up-left)
and some rock position (also up-left).

You can clearly see the difference between both illuminations. The witch doctor is
pretty darker than the demon hunter’s.
As they already stated that there won’t be day&night cicles, I guess they tuned up the
illumination on this area.

Any words on this?

Hrm, well it's possible the witch doctor one was taken in a pre-release build and didn't have final lighting. Possible in time crunches where screenshots need to be taken and approved before an event.

It's possible the lighting was just simply changed as the zones are iterated upon.

It's possible the darker look is from a strong sand storm effect that used to permeate the majority of the area, which isn't present or toned down in the DH screen.

Or it may be some combination of all of the above.

The witch doctor one looks 'wrong' to me, so my gut reaction would be to say it was taken before a final lighting pass happened on that area.