Hey, these are really nice!

I arranged this according to the Wang Tiles 2-edge compact layout, starting with rocky tops. The layout is 128x128 pixels total, and 'alternate' tiles can be selected by adding 128 pixels to the x and/or y coordinates of the base tile. Hope its helpful to someone :-)

Notes on the Wang tile system are here http://www.cr31.co.uk/stagecast/wang/tiles_e.html