dBrand, the most popular custom skin maker for smartphones is now selling skins for the Surface Book (and Surface Pro 4, Pro 3, 3). You can get the skin in different colors and textures, including matte, leather, carbon fiber and wood textures. Here is the one I made:
Of course, you can get even fancier skins that would make your device look even sexier. However, it is worth noting that the skins are quite expensive (a full set for the Surface Book would cost around $50) — but, if you want to give your Surface Book a unique look, you should definitely get a skin for it.
You can get the skins from the dBrand from the links below: