personally i don’t see a problem with the diversity that zbcentral displays. I think that degenerated and disturbed forms generally, and from a technical standpoint, present an opportunity to display ones ability better.
Lets face it, pretty people with no significant details tend to get boring after a while.
With that said, i do believe it is telling of the collective consciousness, that we do live in dark times, and we tend to explore the melancholic nature of our talent, or your talent ;).
But as mentioned above, art has always been a lot about darkness.
Look at how many classic sculptures who have tried to capture the fall of man, in a christian mindset with the garden of eden. great stuff but essentially nothing but “sad” stuff.
it’s deeply imbedded in humans - our dark side. Look at how small children are afraid of the dark, the monster in the closet and under the bed.
How people feared forrest, lakes and pretty much everything we/they didn’t really understand. In the old days, around the camp fire, the most effective way of lingering in our fascination of what scares us, lay in telling ghost/scary stories.
Now the most efficient way is movies or digital art like we have here in zbcentral. nothing has changed that much, we are just better at expressing what we fear or are fascinated by 
so keep it coming. If someone want to display more positive art, which we have a lot of already - do something about it ;)…
http://www.zbrushcentral.com/showthread.php?t=086580
http://www.zbrushcentral.com/showthread.php?t=084909
http://www.zbrushcentral.com/showthread.php?t=072772
http://www.zbrushcentral.com/showthread.php?t=078700
http://www.zbrushcentral.com/showthread.php?t=079352
my 2cents anyway 