You're a hoot. I enjoyed your post as much as your photos. It made me giggle, and all your references to that pizza box made me think of a unique--albeit, terribly goofy-- idea for your border.
Wanna hear my goofy idea? Pizza slices and pepperoni circles. You've got all those triangles that look like pizza slices. You've got the colors of pizza toppings: bacon, ground beef, spinach, tomato sauce, mozzarella, pineapple, mushrooms....
Okay, I'm being silly. You've got that image stuck in my head and right now I'm hungry enough to live 12 years myself inside a pizza box.
Time to think "outside the box." haha.
All kidding aside, I'm thinking the sky blue border first (narrow) then wide golden border to brighten the whole thing up and draw the eye from inside to outside, and bind in forest.