The art is will be availble in spritesheets, so you can change each sprites color.
You can scale & move objects but i don't think you can change the aspect ratio.
Rules:
"The tilesheet will be greyscale. You can change both the foreground and background color (the color of the black, white and grey parts of the tile so you can invert or change each part to whatever you like). Scaling is allowed, but the aspect ratio is not to be changed. (No stretching graphics)"