Spider webs can be painted with spray paint and "captured" on a surface. You can put a REAL spider web on your guitar or motorcycle tank. I've captured webs on simple squares of corrugated cardboard, plywood, even a clarinet case! The pictures I have taken do not do these any justice. They look like intricately hand-painted webs!
Step 1: You Will Need
some corrugated cardboard,
spray paints: one light color & one dark color,
a compatible matte clear coat of some kind,