I think what QuiltE is describing would also be miy idea. Think of a decorative picture frame mat, the old fashioned scrolling type. I'd probably go for a consistently placed large oval in the middle -- some of the pictures would be right to the top (like one of the gingerbread people)... maybe use the Trees for the overall shape, and then just a little swirl in each corner, that should hold enough for anything but heavy use/washing.
And thanks so much for sharing your project with us!