Gearbox is offering SHIFT codes that unlock character heads based on Tiny Tina's DLC. I own the game through Steam and the DLC through the Season Pass (also Steam).
The Gearbox page says:
Look for these customizations to appear in Dice Chests in-game (more on that here) or click on each image above for a SHiFT code to unlock the head for that character immediately -- new images and codes will be posted daily through Sunday, August 18!!
However, I've used the code for both Gaige and Axton but the head has not shown up in my Quick Change machines (nor my inventory). They do show up on my list of unlocked content. Is this a bug or do codes just make the items drop in-game?