I love this! What a great modern baby quilt and good high contrast in the middle will have the baby fascinated by your tumbling blocks. I wouldn't be surprised if as a toddler the baby tries to recreate the pattern with real blocks! I too love how you spilled some of the border motif over into the center part in just a few places. Very innovative.
As far as another border, no! Leave it as is. It looks plenty big enough for a crib quilt and is still a good size for a toddler drag around quilt. Bind it and be done.