Luckily, over at the Last House in America, K S V Woolfoot - who's an expert on the subject, and original author of the artist's Wikipedia entry - has just posted some more GP illustrations from other sources for everyone to enjoy.
I was reading my six-year-old daughter some of these tales over the weekend. After we'd finished the third or fourth one, she remarked: 'These stories are a bit peculiar, because they get quite exciting and then, suddenly, they just stop.' And she's absolutely right.
Whether Peto was sticking to some pre-arranged number of words for each story and thus ran out of space, or whether she simply wasn't terrifically good at developing and ending a tale in a satisfactory way, I'm not sure. I don't have any of her other story-books, so I can't compare.
She did seem to have an unfortunate tendency for introducing some interesting characters and an exciting-looking adventure and then fizzling out and failing to deliver. The illustrations always made up for any disappointment I felt as a child, however (not that I remember feeling disappointed in any way - I always thought of this book as a special treat).