This is more of a case of leaning than trellising but a vine could cover one of these well - the metal thing from a campaign yard-sign.
This metal thing that I've lined with window screen & used as a planter could have been turned upside-down over a vine-ish plant with smaller leaves to form a mass of foliage. Maybe it came out of a deep-freezer?
If the wood shelf, currently laying down to keep some pots from being on the floor in greenhouse, ever breaks, I'm using the sides (coated with urethane) as a trellis.