TheĀ Cas Zeppelin tee design parodies and pays homage to Led Zeppelin's famous Swan Song logo (shown below) by substituting their angel with Cas's likeness instead (shown above). Which is appropriate as Rock is the music of choice and tone of the Supernatural series. Thanks to the Dean character.

Of all the Supernatural fan shirts out there, this one has to on the top 3. No stupid mashups that make no sense just for the sake of making a mashup here. For that, DiHa is nothing short of brilliant.
As for the artwork, it has great colors. As previously mentioned, it is a parody/homage so the design layout is obviously right on the money. But it looks even better than the original version, if that is even possible. Less busy.
This Cas Zeppelin tee will make a great gift for Supernatural and Led Zeppelin fans, without any complaints.
This design is ideal to wear to rock concerts or while watching Supernatural obviously.