All tips received so far will be examined, the police said, declining to provide any details on the information they received.
The photo published by investigators is dated March 13, 1982, and shows a blonde man carrying an assault weapon in a wooded area.
Investigators said the man in the picture is carrying a 12-calibre shotgun manufactured by the Italian brand Franchi.
In a separate appeal to the public launched in 2018, which remains online, investigators are calling for tips regarding a vehicle which got a new paint job after being stolen and a man with an eye-catching birthmark.
The new photo is latest attempt by police to identify the members of a criminal gang — known as The Mad Killers of Brabant in Wallonia or the Gang of Nivelles in Flanders— thought to be behind a string of murderous raids and burglaries that killed a combined 28 people.
At the beginning of the year, police said that hundreds of Belgians would be DNA tested as investigators sought a match to two DNA samples in the file, in a major push to break open the case, which has remained unresolved in the 1980s.