The quote is an excerpt from Leonardo's Notebooks:
"The painter is lord of all types of people and of all things. If the painter wishes to see beauties that charm him it lies in his power to create them, and if he wishes to see monstrosities that are frightful, buffoonish or ridiculous, or pitiable he can be lord and god thereof; if he wants to produce inhabited regions or deserts or dark and shady retreats from the heat, or warm places in cold weather, he can do so. If he wants valleys, if he wants from high mountains tops to unfold a great plain extending down to the sea's horizon, he is lord to do so; and likewise if from low plains he wishes to see high mountains....In fact whatever exists in the universe, in essence, in appearance, in the imagination, the painter has first in his mind and then in his hand; and these are of such excellence that they can present a proportioned and harmonious view of the whole, than can be seen simultaneously, at one glance, just as things in nature."
If you love horses, you might also enjoy learning about Feng Shui Horse Symbolism. Our About.com Guide to Quotations, Simran Khurana, has some perfect horse sayings and quotations that you might like to add to your own horse wallpaper. You can also learn how to create scenes that tell a story with Breyer miniature horses.