The Piece Hall in Halifax opened in 1779 as a trading centre for locally-woven cloth.
Calderdale Council leader Tim Swift said the "fascinating finds" hinted at life in the Piece Hall over the past 230 years.
It is undergoing a Â£19m refurbishment scheme and is due to re-open in Spring.
Three photographs were found behind skirting boards of one of the former shops.
One shows a young boy holding what may be a catapult, standing next to a young girl in a hat. Two other Victorian studio portraits are of smartly-dressed gentlemen.
Calderdale Council said one was a tintype photograph, widely used in the 1860s and 70s.
An un-lidded wooden box was found labelled with Emsley & Collins Ltd, possibly a local company, and a pile of oyster shells was found in the cellar.
Mr Swift said: "The fascinating items provide a tantalising view of a forgotten world. It would be great to know the stories behind them but unfortunately we know very little.
"The artefacts have little historic value but they provide a hint at what daily life may have been like in the Piece Hall during the past 230 years."
In the 1970s, the 18th century hall became a tourist attraction with an art galley, museum and shops.
It closed in January 2014 for a two-year renovation and to add an extension and new visitors centre.
The Â£19m project is funded by Calderdale Council, the Heritage Lottery Fund, Garfield Weston Foundation and the Wolfson Foundation.
Old photos, oyster shells and a World War Two booklet have been found by workmen renovating a Grade I listed building in West Yorkshire.