Pissing about on Steam today I came across This, showing that Brütal Legend along with other Double Fine games such as Psychonauts had recently been added to Valve's Trading Card Beta (which is exiting beta tomorrow). There are 15 cards in total, which, when collected, grant the collector a badge for their profile, as well as the ability to craft these cards into a profile background.
For those who haven't participated in the beta, the way it works is that you get cards randomly by playing the game. You can get a maximum of n/2 cards this way where n is the total number of cards, if n is even then the number of droppable cards is rounded down. After this, you need to either trade with other people for the cards or wait untill you get a booster pack (which are given randomly) which allows you to receive another 3 cards in whichever set you received the pack for.
The available trading cards are as follows and each depict concept art from the game. (Sorry I haven't got any of them yet so unless someone else has you won't be able to see them properly here I will however, update them as I get them, if anyone else has/gets them feel free to contact me with images of them.)
I have to say I dislike that some of the cards contain spoilers. And the bladehenge card calls Ironheade "Ironhead". Someone needs to put an E on the end so we know they're not screwin around.