Exercise : head back to the demo you have done making a virtual room of our current location. Think about each entity you used. Close that demo (yes, there is a button for that) and in the new one
scavange the net, or better even, make your own texture. That's right you will have to start your favorite drawing software and take 5min to draw the best texture you can, we'll then upload it and you can use it in your scene.
Think about our texture can trick the person having the experience. Appreciate how much more depth and graind a scene has using texture with imperfections rather than perfect fake colors. Consider how textures can also be use not just for colors but also to change light reflection.
Extra exercise : try at least 1 partly transparent texture. Try also a normal texture but applied on a partly transparent object. You don't know how, well you should know the drill by now, cheat!
Done? Go back to learn more.