I've got 11,637 Cubs cards from 82 different brands listed on a spreadsheet. A random number generator picked five cards, one each from the past several decades.
1950s / 1960s: Topps 1957 # 378 Elmer Singleton This picture was taken in Philadelphia's Connie Mack Stadium (that's the "Spite Fence" in the background) during the 1957 (the only year the Cubs used the road uniform he's wearing) season, probably May 2-4. Odd thing about that visit is that the series was a Thursday - Saturday series. On Sunday the Cubs were in New York. It never happens today that a team splits a weekend between two cities.
1970s: Topps 1971 Scratch Off Glenn Beckert Topps put out scratch off games in both the 1970 and 1971 sets. They used the exact same checklist both years, 24 cards, one player from each team. The fronts and backs are identical. The only difference in on the inside, where the '70s have a white background while the '71s are red.
1980s: Donruss Baseball's Best 1988 #149 Dave Martinez The Baseball's Best set was a 386 card parallel version of the Donruss Base, with orange instead of blue in the border. Martinez spent just half the 1988 season with the Cubs, and then was traded to the Expos on July 14. Google "Cindy Sandberg Dave Martinez" to find out the alleged reason for the swap.
1990s: Star Platinum 1990 #173 Mark Grace This is one of nine cards of Grace in the 1990 Star Platinum set. The 1990 season was only his third in the majors, but his performance in the 1989 NLCS (he hit .647!) pushed him into the spotlight. Grace hit .309 and knocked in 82 runs in 1990.
2000s: Heritage 2004 #297 Carlos Zambrano Heritage gives us a young and relatively sane-looking Zambrano. Injuries to Wood and Prior during the 2004 season pushed Zambrano into the role of staff ace. He tied Greg Maddux with a team-high 16 wins and was named to the NL All Star team