I was thinking of Christmas trees, the same as bjchad. There are books with continuous line quilting designs. I got one free with my AQS membership this year:
https://shop.americanquilter.com/826...-patterns.html
I also wanted to mention that sometimes it's nice to not be able to see the quilting in the border. It gives more freedom to try out designs & not worry about them being perfect. That said, I did that on my first FMQ quilt ... stippling in the middle & a custom vine design in the border (I looked through photos of leaves on google & picked one, then created a triple leaf design for the corners & just drew a basic vine with random leaves along the edges). I picked a thread to hide it, but as I already had all that practice with the rest of the quilt, the vine came out beautiful & I was pretty disappointed that it was nearly invisible. You might consider picking a contrasting thread if you have a really cute design in the border. You can definitely switch threads & use a white or a color on the black and have it really stand out.