I liked it LW; but wondered about your 'theme'. Most artwork that has really struck me has some kind of message or theme to it.
Why don't you make the castle into a shadowed mosque & the Mt Rushmore faces feathered into the sky staring down in dismay/astonishment while laser beams from the towers (painted in US colours) blast into the mosque.
Could be powerful or irreverent, depending.
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh