Since you aren't comfortable with free motion yet, I'd suggest you do a piano key in the border. Put some pins in there to stabilize things, then stitch from your narrow border to the outside. This will tie your interior to your outside, and give you some nice texture.
If you were more comfortable with free motion, I suggest a lacy curved feather. Your fabric is busy, so the detail wouldn't be noticed, but the texture would.
Have fun, and don't forget to breathe!!!