The 1984 set was Jewel's fourth set. In each of the previous years, 1969, 1973, and 1977, the Cubs collapsed just about the time the pictures were being released. The '84 Cubs didn't fall apart, and managed to win the Eastern Division title. (The collapse came in the NLCS, but we can't blame that on Jewel, can we?)
As I look over the complete set of pictures, I can see that there are three distinct types.
First, there are those of players that were with the Cubs at the start of spring training.
Except for Larry Bowa, they all have a blue background.
Then there are those that show players picked up at the end of spring training.
They have a gray background and cropping issues.
The third type would be the players acquired during the season.
I'll end with a tile that shows all 16 players, grouped in rows for the week the pictures were issued.