The Allegory of Law and Grace by Lucas Cranach the Elder is a great example of the first principle I mentioned above. This woodcut print is a visual embodiment of the differences between Protestantism and Catholicism. The picture is divided in the middle by a tree, the left side is representational of Catholic beliefs and on the right is that of the Reformation. Cranach depicts the former as damnation despite good works motif, with the skeleton jabbing the born sinner into the flames of Hell and creating the Savor as unforgiving by the sword jutting from his head. The latter is the side of Grace or the Reformation, where the Savor is showering the born-sinner with rays of forgiveness. This is alluding to the Reformation's belief that the individual's redemption is through God, alone.
The second principle of the Reformation is best seen in Albertch Durer's painting, Four Apostles. The emphasis on the Bible as the word of God is best noted in the way that the four men are pointing to the book opened to John 1:1 which, the text reads, "In the beginning was the Word, and the Word was with God, and the Word was God". Essentially this art work is propaganda for the Bible, which was believed to be the direct connection with the Lord God.
The third and final principle of the Reformation about the scaling of the Sacraments can be seen in another of Durer's woodcut works called Last Supper. in which he depicts the Christ as being there, being human among his apostles. The Reformation insisted that Communion was merely a representation of Christ's body and blood, therefore in this woodcut print, at the bottom right there is a jug and basket full of bread in the same room as Christ, giving the Savor a very human experience within this print while symbolizing the change in Protestant's idea of Communion. Also, in previous works of the Last Supper, there is a sacrificial lamb spilling blood onto a plate while in Durer's print there is simply an empty plate.
These are just a few examples that I found in the book that best illustrate the three main principles of the Protestant faith during the 16th century.