If this is your first attempt at machine quilting, you might like to have the backing similar colours to the front, so that it won't be so noticeable if some of the front thread or the back thread tension isn't quite perfect and pulls through to the other side.

You could try laying or hanging the yellow by the top to see what it would look like...leave it for a day or two, even? OR Take pics and look at them on the computer, then see how you like it.
I'm sure you can do a wonderful job quilting a flower in the blue!

you could pick a few you like take pics post and let us vote on it if your not sure of your own judgement. I have confindence that you'll pick the perfect match for the quilt

Thimblebug the small squares in the patch look like they have some sort of border but it is actually the sun shining and creating a shadow on the seams. Also I have machine quilted before, 3 other queen sized quilts, many baby quilts, plus lots of smaller pieces, it's just such a struggle to sew where you need to on my machine - possible but difficult. The batting I use is warn and natural - all cotton, it's pretty flat as well.

Sandra- I'd try to echo by extending the lines from the patches into the blue but I doubt they are truly that even!!! (Ha! and I've read the comment that someone posted ~ I meant for it to be like that!!!).

I'm excited to try a flower design and will have to find some interesting contrasting thread to use.

Very nice, unique. Alot of work, Your quilting suggestion is a good one to. Great job.