I have done a lot of cross stitch in the past and have used many as pillows or in a wallhanging.
I would not recommend in a quilt that is to be used and washed a lot as I don't feel the stitching would hold up and I am very much opposed to putting a fusible interfacing on the back because as time goes on it will turn your cloth an aged brown tone.
Consider using them in pillows or as wallhandings framed with fabrics/
Good luck