For example, Victoria's 18th century dress has an extra set of sleeves (ruffled ones) that can easily replace the tailored sleeves she mostly uses. She also has a pleated collar. These small things can easily get lost, so I'm making her some bags that can hang on the hanger with the costume.
I simply cut some muslin rectangles (mine are about 9 x 11 inches) and serged three edges together. I have also made shoe bags for her to use at Dickens Fair where at the end of the day we are frantically throwing our costumes in a box and have shoes that are filthy.
As you can see from the photo below, I was able to use some scrap fabric to make a matching one for her 18th Century gown. Now all her pieces are hanging in the closet together!