One of the dangers of producing a number of insert sets (or, in the case of the junk-wax era, small boxed sets) during a given year is the lack of continuity between them, making it darn near impossible to remember what year each insert was released. I certainly don't want to see every set homogenized, but how about a motif in the design- some pattern that ties each insert set to the base set.
I've never been a big fan of Fleer, but one thing they did well, even if only for a couple of years, was create boxed sets that somewhat mirrored what they were doing with their base set. This is most evident in 1988 and 1989 Fleer baseball.
Fleer made heavy use of stripes/lines in their designs for those two years and the results were some of my favorite offerings from the company- behind only the 1994 Fleer baseball product.