Here's my latest creation. A mosaic made of 1x1x 2/3 slopes [cheese wedges] that are combined with 1x1 plates to make a custom palette of about 28 colors.
The piece is 64x64 studs in size for around 4000 cheese wedges! Actually, it's a bit less than that because of the black tile background but there's still a LOT of them! And around 1500 of those wedges sit on top of a 1x1 plate. So, roughly speaking the part count is around 5500 pieces not including the 128 4x8 white plates I lay down first as the background.