you can make patches with scrap fabric or old clothes and acrylic paint :]. You can use fabric glue to attach the patches or sew them, but I think using both keeps the patches on better and looks cool. Just don't use hot glue because it'll just peel off lol.
I made some out of an old pair of jeans and they looked great!
if you want some ideas there's a bunch of stencils on r/AnarchoStencilism :]