Shadow boxes are good with acid free backings.Here is an address from a couple who display them at one of the largest craft type shows in Alabama. Debbe & Greg Shirley,2004 King Court, Fultondale, AL 35068, 205-841-8077, Shadowboxgirl@netzero.com

They have them 1 5/8" deep or 3" deep or will custom make for an extra $5 per inch. 6x6 is $6 all way up to 18X24 at $35. She provides explicit directions for setting up your
display. They do mail but there is no listing about charges.

I have a couple for some of my mother's sewing things...scissors, pin cushion, thimbles & etc. Instead of using the mat backing, I purchased pictures from another vender of an antique sewing machine & one of an elderly woman's hands while quilting.

I have a Sturbridge kitchen towel from early 70s I put in a poster frame backed with fabric left from a pair of wool slacks I made...one of those happy discoveries. The towel is centered on the charcoal wool fabric that serves as a mat and makes a stunning display.

You might be able to do the same with a coordinating fabric for the mat in a size frame appropriate for the pillow.