I see that Ladybird have now started to sell prints of their artwork archive:
There are hours of fun to be had here, browsing through some wonderful prints. I think I would have spent quite a lot of money here once upon a time, before I developed an expensive taste for the original artwork.
One thing strikes me as strange, though. I notice that the artists aren't credited on the site. The author of a given book is credited even though the text is not reproduced, but not the artist! Hardly seems fair.
Also, I wonder what they mean when they state that the artwork comes from the 'Ladybird Archive'. I assumed at first that this must be a physical collection of artwork which Ladybird (Penguin) hold - as I know they do. But the fact is that there are prints on this site, the original artwork for which resides in my living-room, so that can't be right.
Anyway, have fun browsing.