Remember that bat-a-rang you made earlier in step 3? Use your acrylics to paint it "black" and spray it with clear spray paint. Then wrap the hemp twine around it in an X pattern and use construction adhesive to glue it in place on Batman's shoulder bag.
For Robin, take 24 inches of hemp twine and neatly coil it up. Then use construction adhesive to glue it onto Robin's shoulder bag.
Take some of the buttons and buckles that you gathered and glue them to the gnome's shoulder bags and jacket cuffs.