52 Grosvenor Gardens, SW1

As construction of the Midland Bank HQ (see below) was proceeding (it took fifteen years!), Lutyens got another commission for a facade, behind which lesser architects would do the boring bits.
This was for a speculative office block opposite Victoria Station, built by the Duke of Westminster. Lutyens got the job because he was best mates with the Surveyor of the Grosvenor Estate, fellow-architect Detmar Blow.
The facade is neo-Classical, just like the Midland, and frankly a bit dull, although the recessed main entrance with its giant Doric columns has a spark. It was originally called Terminal House but was simply numbered after a recent revamp.
Little heads enliven keystones all over the building. One, above the front door, is a fierce face in a helmet surrounded by foliage. The helmet is very familiar but I can't place it. Tibet? South America?
My complete ignorance of botany means I can't identify any of the plants either. The man with the whacky beard on the left seems to be surrounded by grapes. Below, the serious guy has poppies, I think. I suspect they are all native crops and headdresses of a particular place. Anybody have any ideas where?