Most of the Mystery Box pieces have red sold stickers although Rayner said he is replenishing the works.
"There is a cash and carry option so some people have already taken theirs home."
Rayner and his brother Paul moved from their Guyton St gallery to the converted Glasgow St villa owned by Bryce Smith and Sue Cooke in August 2017.
As well as the Rayner Brothers' Gallery, the arts centre houses Gallery 85 for guest exhibitions, studios, the Cuban Belle Cafe and a flat and studio for artists-in-residence.
The Wally Kirby exhibition Mid-Century Modern is showing at Gallery 85 at the moment and Rotorua painter and sculptor Sarah Zeissen is the current artist-in-residence.
Mystery Box is open for viewing at the Rayner Brothers Gallery from 11am to 3pm each Wednesday to Saturday until November 17.