Your print panels are busy enough that anything you quilt in them isn't really going to stand out. I think that for a quilt like this you'd be looking for texture, which you could do quite nicely with an nice edge2edge design. I'd probably match my thread to your background as it is quite dominant and it would still blend in with your print panels. If you are thinking more custom style, where you isolate your borders and panels, I'd keep it quite simple in the print panels, like a cross hatch that is easily done where visibility is an issue as you stitch and pick a nice back ground fill. Saying that, makes me suggest you could isolate your border with stitch in the ditch on each side of your stop border and do a nice border treatment and then still do an e2e on the inside, what I call a partial custom treatment. That's my 2 cents! Some things to mull over
. Look forward to seeing it finished!