I have an account I no longer play on that has an extremely rare unusual courier, which is a 2012 Frostivus Frost effect on a Prismatic Drake. Also, the rest of that inventory is for sale preferably in bulk.
The drake is worth around $40, there are not a lot of them in existence since Frostivus was a one time deal and the Prismatic Drake was released towards the end of the event, making very few unusual drakes with the frostivus effect pop from loot boxes.
If anyone is interested please let me know soon, I am going to sell it for cash on the community market otherwise.