If I am understanding what you have done here, you are going to create appliques on a whole cloth quilt. If you want the seams on the inside, you would have to cut the whole cloth (background fabric) into appropriate sizes for each "patch" and then sew those together. I don't see a problem with the way you are doing it, you will need to secure the edges of the patches down. Sewing around with just a single stitch might not hold up under wear and tear. Either a satin stitch (really tight zigzag) or a regular zig zag would be better than just a single stitch. Depends on the look you want and how much time you want to spend. If you turn the edges under on each piece it would be neater, and then a single stitch might be sufficient, but I might still do a zig zag. You've done a great job on placement and colors are awesome! Good luck!