Green and silver is a quieter pairing than the gold-and-jewel-tone combinations most carved beds reach for, and the reason it works is temperature. Green sits on the cool side of the spectrum, and silver leaf is cool too, so the two agree; gold would introduce warmth and the eye would read the green as slightly grey by comparison. Choosing metal to match the temperature of the fabric is one of those decisions that is invisible when it is right and impossible to ignore when it is wrong.
The small patterned medallion in the crest solves a different problem. A large field of a single strong colour loses interest at a distance - it becomes a block. Setting a patterned version of the same colour into the crest gives the eye something to travel to, so the headboard holds attention across a room.
Our master Indian artisans build the crest opening to that medallion before the frame is finished, so the pattern lands square inside its arch rather than being trimmed to fit afterwards.