The phrase "old suitcases" refers to bags or containers that people used in the past to carry their belongings while traveling. It implies that these suitcases are no longer in use and may be outdated or worn out. Full definition
«Shop» is a small old suitcase that has shelves built into it and rows of colourful threads, scissors and needles. (treehugger.com)
This bedroom, for example, makes good use of a pair of lovely vintage nightstands and a pair of old suitcases given new life with a coat of bright blue paint. (thespruce.com)