Head base for the jerboa fullsuit I've been working on. I normally don't build off helmets, but the client requested it and provided the helmet. The mask will still have a moving jaw, just using a different rig than I usually make use of.
These days it's not done as much, but I know there were at least a few suits with heads built off helmets about a decade back or more that were made by other builders. The method is better suited for oversized heads (think sports mascots) as the helmet provides a solid contact point with the wearer and makes the costume's head move with the wearer's movements.
Link
Raja The Tiger
hmm, never heard of heads being made off of helmets