Looking good. I can see improvement between your 1st and 2nds photos. My bqf (best quilty friend) uses her practice pieces to make hot pads, mug rugs, placemats, etc. She cuts them up just like batting, sandwiches a couple layers between fabric and orphan blocks or scrap fabric, then binds them like a mini quilt. Nothing goes to waste.
You can also note on your different practice pieces which thread and batting you used, tension settings, etc., and keep it for future reference. Every time I start quilting a new project I use a practice sandwich to warm up on. Sometimes I use the same one over and over till it's so heavily quilted it's stiff like cardboard, then I start a new one. I haven't yet found a use for those stiff pieces, purse bottoms maybe?