Johann Wolfgang von Goethe was a huge influence on development German lied with his literature. These were some themes that were found during The Age of Goethe were the following:
1) The artist as the Wanderer - Cast out from society. This is found in Schubert Lied.
2) Reveling in Nature, coupled with isolation from human society.
3) Love of the past and of the exotic. Ideas from the Greeks, Romans, Persians, Shakespeare and the Middle Ages. Hafiz was a Persian poet who Goethe admired.
4) Super Natural forces. (Ghosts, fairies...etc.)