I've been using this design for the regimental standard for years. It is based on the Royal Pavilion in Brighton. It is a popular piece of imagery, and even looks quite cool in green (as used by Brighton and Hove council).
The 4 guardsmen are from the 40K Praetorian XXIV box set. The officer is the "disgraced commissar" from the Schaefer's last chancers box set, with the lasgun replaced by a close combat knife. The Chimera is actually a software CAD model that I rendered into the background.