The first, of General Grievous, was built with 3595 plates on 3 x 2 48x48 Baseplates. He looks very menacing:
My favorite is the second, of Aayla Secura. She was built with 5377 plates on 3 x 2 48x48 baseplates.
Oliver has several other mosaics in his photostream, too, including this lovely mosaic of Neuschwanstein Castle built by visitors to Bricking Bavaria 2011:
