This is an artistic T-shirt based on Erlkönig, Franz Schubert's best-known song, composed in 1815. The song is based on Johann Wolfgang von Goethe's famous poem, written in 1782, which is in turn based on an early Scandinavian legend. The lmage is by the German painter Carl Gustav Carus from 1832. For more information, there is a page about Erlkönig on Wikipedia. 

The image is the same on both the front and the back.