The basic imagery is optical data, yes.

However, if you download the Microwave Sky layer from the Earth gallery, you can see the sky in microwaves. This view is very important to cosmologists, but the really cool thing about it visually is that you can see that places in the Galactic plane where the sky is dark thanks to dust extinction, the microwave sky is glowing brightly thanks to the thermal emission from that dust. Also check out the locatio of the Orion nebula and the Magellanic clouds.