Can I use homespun on the back of a regular cotton quilt?

I would say yes you can. Be careful of the raveling though. I would probably use a little wider than 1/4 inch seam and/or use a smaller stitch lenght to make it more secure.

thank you!

pre-wash it- it will shrink= more than flannel- it is a looser weave.
and if you have to cut it you may want to starch it well-
homespuns make very cozy soft backs- they are great to use in the top of the quilt too
if they are thin a stablizer may be needed- but i have found if i pre-wash -toss in a hot dryer= when they come out they have much better body- more substance- the starch is because with the looser weave the fabric stretches easily= the starch will help keep the stretch to a minimum