My current answer when asked for picture book recommendations is "Anything by Emily Gravett," and here's why: I haven't yet come across one of her books that I haven't liked, and they're big hits with the boys too. All her books are beautiful, as befits someone who has twice won the Kate Greenaway Medal for illustration, and the stories are equally charming.
Fils cadet is particularly taken with Blue Chameleon at the moment, while Fils aîné prefers Again!
Again! introduces a scenario familiar to every parent and child at bedtime. Cedric the little dragon has one favourite story, and he wants his mum to read it. And again, and again, and again! Dragons being what they are, when Cedric loses his temper, the results are startling and very funny. Fils aîné thinks so anyway, bounding around with excitement and bellowing "again!" I, on the other hand, find myself entirely in sympathy with Cedric's mum, wearily changing the story with each repetition before falling asleep herself...
Both of these are books we've had out of the library before, and have out of the library at the moment, and undoubtedly will have out of the library again in the future, given the rapture with which they were rediscovered last week. Others that I'd particularly recommend are Meerkat Mail for older children and Orange, Pear, Apple, Bear for younger ones. But like I said, anything by Emily Gravett is bound to be good!