I have just printed out my first photo fabric picture. I followed all the directions and a tip from a board member using fabric glue solution to prevent fading. All went well, here is my question: Do any of you back the photo fabric with muslin? thanks

No. I've never needed to use anything other than the photo fabric. I use Printed Treasures, which is the same weight as my quilting cottons.
Besides, why make more work for yourself? :-)

I used June Taylor, seems heavy enough

Depends on the quality and weight of fabric...I've used some June Taylor that's very light and I use Lite heat bond to back it to muslin.