Mystery Shack Poster

It’s been a long time I’ve been wanting to decorate my office walls with my very own original artwork, but I haven’t come up with a good enough of an idea so far. What can I draw that it is worth framing and hanging on the wall?
My niece told me I should create a Gravity Falls poster. Although it isn’t something I’ll hang on my wall, I decided to take the challenge anyway.
I thought the best way to do it right would be making a fake ad for the Mystery Shack, in which you’ll see what the Mystery Shack has to offer: The pre-teen Wolf-Boy (Dipper in a werewolf costume), Questiony the Question Mark (the Mystery Shack mascot) and the delicious Mystery Dogs (corn dogs shaped like Question Marks. How they managed to get them into this shape is well… A mystery!)
The result: One happy niece and two 24″x16″ posters.

One of these posters is now hanged on my niece’s room’s wall. My walls on the other hand will have to wait for an inspiration to come. Got any good ideas?