I would add a narrow black border like the others to continue that repetition. For the outer border, I would keep it rather simple to throw focus back on the center. By repeating some colors from the center in the outer border it would bring more balance overall. I would start with the light blue (background of the cardinal block), the darkest green from the leaves, charcoal or black. I'd have to audition them to see what would work best.
The mock-up was done in EQ7. The border is from Auto Borders, Single Block Patterns 1-6. There are some other borders in that section that may work too.[ATTACH=CONFIG]393805[/ATTACH][ATTACH=CONFIG]393807[/ATTACH][ATTACH=CONFIG]393808[/ATTACH]