I learned something new today. Thanks!

The quilt I'm working on now has a narrow strip in the border. I decided to try out one of the decorative stitches on my Bernina in a contrasting color.

If you don't want the contrast, you could match the thread with the fabric.

I would think if you SITD around all the panels, that would be enough. Maybe something like loops or zig zags. It would be totally up to you.

Check your batting. It will tell you how far apart the quilting needs to be to hold up and not bunch. I really like what you have done so far, and would recommend you put additonal quilting as needed. I know most batting is between 3-6 inches apart.

Thank you for asking this question. As a new quilter I had never thought of that. I will be watching all the answers from the "experts". Thanks again for asking this question.

I guess I quilt a lot heavier. I'd suggest that your 'pebbles' fabric be quilted a bit more. I would make rectangles, about the size of my palm. It wouldn't take a long time, and it would continue the concept. You would make it look like a rock wall. I would not make the rectangles have sharp corners, I'd make them rounded. For quilting motifs, I have a card file that has many different motifs, for free motion, I divide them up into rounded, meanders, feathers, sharp points, etc. I've found that it really improves my quilt if I add various related motifs.
Good luck.

Thanks for the info!
I've just been doing the "channels". I had been doing wavy sort of diagonal cross hatching, then "somebody" said don't let a line of quilting cross another so I quit.

Thank you for the question. I would have thought it was ok but after reading ckcowl and Buckeye Rose responses, I've learned something and it makes sense