We just completed this cool custom armature for artist Jess from supplemonstrous: http://supplemonstrous.tumblr.com/
It was definitely a challenge because of how large the head was and it also forced us to make some decisions about how horns will work. Essentially horns will be separate pieces so that artists can arrange them wherever they want and either temporarily fix them with clay or permanently with our hacker kit (yep, just posted this last night on Kits and Bits pages).
This also finally forced me to get around to building a horn creation tool in the event more customers request custom horns with their custom armatures (www.armaturelab.com)
Btw this head model is actually the same model as our generic human head found here
All we did was build a head customization system so we can manipulate the geometry to match placement and proportions requested by customers.