There doesn't appear to be an online image collection like the one in Manchester. To see old photos of Salford it's necessary to physically go along in person to the Local History Library in the Art Gallery building, next to Salford University, and have a browse through the archive. The Local History Library page is at the URL below:
Visit Salford Local History Library - Salford City Council
I intend to call in there soon. I've been in Stockport and Trafford local history libraries. They have a great resource but it isn't always available online.