Sorry, no screenshots as Yammer hosts company stuff and I'd rather not inadvertently post up something someone wouldn't want me to. However, the style is quite small -- just give it a downloand and try it if Yammer is burning your eyes.

changelog:
20131008:
- update for white heading bars -- now to dark with orange text.

20130917:
- update for chat account list

20130813:
- style invitations dialog
- add border radius to replies container & navigation links containers
- style user profile header pane
- make conversation hide option clickable visible
20130805:
- initial release