A repeated, recurrent theme associated with an idea, situation or person–whether it be an image, motif, stanza, phrase, or melody.
If you’re in the business of making beautiful furnishings, it’s a good idea and a nice touch to have a subtle leitmotif that appears now and again as a kind of signature. It can be anything, for example the 18thC Dutch-British wood-carver Grinling Gibbons famously identified his work by including carved pea pods as a trade mark–legend suggests a closed pea-pod indicated payment was still due, whereas an open pea-pod meant payment had been made.