The use of posters in a comic book is nothing unusual, and Carl Barks drew them frequently in his stories. But he often took them to a higher level, because he made them worthwhile to look at. Although some were no doubt drawn to be used as mere filling, they were often very funny, and some could be read in different ways. Others were placed in the background so as to be so inconspicuous that you would hardly ever notice them. They are often the best!
It is not the intention to list all of the countless ordinary posters and notes Barks drew in most of his stories. You will 'only' be shown a very small collection of the more inventive and unusual ones. And there are more scattered all over the site - see The Injokes for example...

FC0282 Lovable as always...	WDCS148 ...even at Christmas Time!	WDCS158 The Junior Woodchucks' Code!
U$47 Benny Badman Orchestra (=Goodman)	FC199 Self-portrait!	WDCS049 (Observe the unusual sequence of HDL...)
WDCS149	WDCS160	U$32
U$38 Joe Snake for Congress	WDCS278 Inside the Quintagon (=Pentagon)	FC0386 O.U. Drip
U$63	FC0199	DG26
DG26 Self-portrait!	WDCS176 Billy the Kid	WDCS060 Oh, Bummer...

EXTRA

You may agree that printed signs and billboards are a sort of hardcover posters, and as such the selection presented below should be perceived.
Again, you will not be presented to the most ordinary ones among the business, shop, or sightseeing signs.

WDCS149	U$48	WDCS060
DG26	WDCS159	DG26
U$28	U$35	U$38
WDCS064	WDCS063	WDCS249
U$55	U$08	U$35
U$38 Still No Sign of Improvement...	WDCS135 ...Anywhere!	WDCS250 Signing Off...