At my company one employee took the effort to take a profile picture of every employee. He only took photos where people smiling, it took some time but within few weeks (100+ employees) it is done.
Then everyone was asked to replace their profile picture in hipchat/google apps/yammer to the one taken.
Everyone agreed, and as a result I only see smiling faces in the apps these days.
It feels good.
Smiling pictures make a difference.