This is what I did to upgrade them...
Foam core board
Old Styrofoam sheets
Start with your old suitcase...
Measure the length, width and depth of your suitcase bottom. Cut Styrofoam to fit the bottom of the suitcase. This will allow your foam core to be even with the top of the suitcase. Place a brick in the suitcase bottom, if needed to give it some weight and keep it from turning over when you are using it.
Measure the inside top and bottom of your suitcase and cut foam core board to fit (cut just a little smaller to allow room for fabric to fold over board).
Cut you fabric a little bigger than the foam core so you have enough to turn over to the back side of board.
Spray the board with spray adhesive and quickly lay your fabric on the board and spread out to get rid of wrinkles. Spray the outside perimeter of the back of the board and smooth fabric over the edges to the back so that no frayed edges show.
My jewelry has a vintage, heirloom aesthetic so, after applying the fabric to the board, I also sprayed the back side of doilies and adhered them to the fabric covered board.
When finished, spray the back side of the foam core and quickly place in the suitcase and apply pressure to glue the foam core to the inside of the suitcase.