I think the loops on the back are a tension issue combined with your FMQ motion technique. You can also see how the quilt puckered up a bit on the quilting lines, which shows tension. You probably need to slow down a bit on moving the quilt under the needle. We were practicing FMQ at our friendship group last night, and I was surprised how nearly every person new to it were trying to go way too fast. Start at a slower stitch speed on your machine (if you have a speed setting - or just don't push all the way down on the pedal) and don't go so fast. I like the quilt...the colors and how you used the fabrics is very nice!!