You can use ABSOLUTELY ANY pieces of fabric for the Rag Textiles Workshop, BUT, you may not have a small wire brush nor an embroidery hoop.
This sample pack contains:
 
3" embroidery hoop
Wire brush (brass) 12" handle
Mixed fabric scraps (approx 3" square)
Small selection of Bangladeshi Chindi rags
4m of Sashiko Thread (variegated 173)