Editor: Since it's not easy to find one image to represent the game, I've done one icon for each faction, so you can choose your favorite
They're Vista ready and includes the following sizes: 16x16, 24x24, 32x32, 48x48 & 256x256(PNG Compressed) in RGBA (32 bits) & 256 (8 bits).
256x256 PNG files included for Dock icons.