In the 1980s, Penguin's usually high design standards seemed to desert them for a while. Even the company's official design history, Phil Baines's Penguin by Design, admits this, noting of management directives at the time that "their effect on the cover designs might best be described as 'varied'. By the early 1980s many Penguin books, with their insensitive combinations of type and image, looked like the cheapest in the bookshop."
For the final five books in the Penguin Decades series (see the 1950s here, the 1960s here and the 1970s here), artist John Squire (once of the Stone Roses) was approached to do the covers. I mentioned before that I was a bit trepidatious as to what he might come up with, given that I'm no fan of his art (which often seemed to desperately ape Pollock and the like, without adding anything new). But these covers are actually very nice. The have the feel of earlier Penguins, while also suiting the 1980s as well--they're what Penguin books of that decade might have looked like in an alternative universe of wiser design choices.
As an example, here are a couple of the original '80s paperbacks.