Dr. Seuss wrote and illustrated If I Ran the Zoo. Yeah, he's one of those irritatingly talented guys.
As one of Seuss's earlier children's books, If I Ran the Zoo contains illustration that seems to occupy a middle ground between his children's books and his career as a political cartoonist. What's political cartoony about it? Exaggeration.
These Seussy illustrations make the words on the page shine. First, they show children how even simple words can create wondrous imaginings. Take the lines: "I'll bring back a very odd family of deer: / A father, a mother, two sisters, a brother / Whose horns are connected, from one to the other" (16.2-4). We could picture a family of deer with their horns intertwined no problem, but the picture attached to the words really pushes our imaginations toward something wild, weird, and new. The intricate design the deer's horns create is something pretty phenomenal to see. The illustrations help demonstrate how to push your imagination beyond the barest meaning of the words.
Second, the illustration can help the child even imagine the thing at all. Take any of the following animals: a Bustard (10.3), an It-Kutch (32.8), and an Obsk (30.2). What the heck are those? Well, the pictures will show you. When faced with even simple words, children can sometimes have a hard time conjuring the respective thing the word is meant to represent. Faced with made-up words? That can seem too daunting. The illustrations give us a way to see what exactly the word represents.
Now, we aren't suggesting that the illustrations are doing the heavy lifting for the child. They aren't taking over his or her imagination and doing all the work for them. What they are doing is demonstrating how the imagination and words are linked together. Words are limitless and so is the imagination. If you imagine a new creature, then you can make up a new word for it or connect a new series of words together. The reverse is also true.