I think it looks great as is. :) Only thing I would change is the green border pieces that close to each other? In the top right hand side and the bottom middle? That being said, you dont want the greens to meet with the other block either I would guess... so maybe leave well enough alone?? lol... :)
The additional border would be pretty maybe? And that would also break up the ivory corners? But hard to tell with out looking... :)