My main suggestion would be to follow your inspiration. It is so personal, so, I bet you can draw some great non-cliche ideas there.
My personal associations with Greece and the image on the deskmat would be: an olive branch (or just an olive), a small fishing boat, the sunset in the sea, the shape of the Peloponnese and/or Crete, a branch of thyme, the Bouzouki, and of course the building style with lots of interwoven cubic shapes and some domes, as well as ornate wooden doors (this is probably very hard to capture in novelty, though). To me, all the references to ancient Greece (columns, pantheon, statues) are not as strong/too cliched, but if these are strong associations for you, I can totally understand that.
I guess it might make sense to decide what aspects of Greece you want to focus on, to make the theme stronger and more coherent.