I've got 9,145 Cubs cards from 56 different brands listed on a spreadsheet. A random number generator picked five cards, one each from the past several decades.
1950s / 1960s: Bowman 1950 #107 Dutch Leonard: The Cubs picked up the 40 year old Leonard from the Phillies for the 1949 season. Starting 28 games, the veteran went 7-16 with an ERA of 4.15. The Cubs decided that Leonard was no longer a starter, and he spent the 1950 season in the bullpen. That rejuvenated his career, and he was 5-1. He would hang on with the Cubs through the 1953 season, when he was 44 years old.
1970s: Topps 1971 #704 J. C. Martin The Cubs acquired Martin from the Mets late in the spring of 1970. Starter Randy Hundley was injured in April and missed most of the season, making the trade for Martin seem pretty smart. He played in 40 games, but hit a miniscule .156, making the trade for Martin seem pretty dumb!
1980s Circle K 1985 #10 Ernie Banks Mr Cub! This card is from a set produced by Topps and sold at Circle K convenience stores. The set was called "All Time Home Run Kings" and had a card for the top 33 career home run hitters as of 1985 (except for Ted Williams, who was left out because of licensing issues). Ernie's card was #10 because at the time, he was tied for 10th place with Eddie Matthews. Today, Ernie and Eddie have dropped to a tie for 21st place.
1990s Leaf 1993 #224 Ryne Sandberg It looks like Paul O'Neill is trying to break up a double play at second. This was May 8, 1992 (the brown ivy helped me narrow it down). O'Neill led off the fifth inning with a single, and then Chris Sabo hit into a 6-4-3 DP. The highlight of Sandberg's 1993 season was on May 26th against the Giants. For the first time in his big league career, Ryno was tossed out of a game, arguing a force-out call in the bottom of the fifth.
2000s Topps Traded 2003 #51 Lenny Harris Did you realize that Lenny Harris is baseball's att-time pinch hit leader, with 212? I didn't. The Cubs picked up Harris as a free agent in January, 2003, to obviously boost their bench. In 75 games, he hit only .183 which wasn't much of a boost, and on August 2 the Cubs released him.