I wanted to do a combination of my childhood cartoon concept in a van. I imagine Mabel and Dipper found an abandoned Mystery Machine van. With Mabel's personality, she would decorate it with all her stickers. But when Stan, Dipper and Mabel went for an adventure and got lost, the van has been abandoned. 

I added a couple of stickers from Mabel's sweater, and the driving licence on the glass because I think in the Gravity Falls' universe, they definitely would be able to get pass the officers. I also think its funny.

Surfacing - Substance Painter
Rendering - Marmoset Toolbag

Van model courtesy of Christina Ryan
Mabel's stickers courtesy of Gravity Falls.