I also like the idea of black sashing, black inner border, and if possible use some of the original fabric as a wider outer border.

But if I put sashing, won't it break up the picture and spoil the effect of having a new representation of that sunrise in the jungle type place?

Yes, it would be an entirely different look with sashing. It would just be a way to make the quilt a lot bigger without resorting to lots of borders.