A Sound of Thunder did originally contain comic-book style illustrations. The pictures do help convey the tone of the story. In the beginning, the pictures are bright and cheery, full of wonder. We see scary dinosaurs, but with bright yellows, purples and greens so the overall image is more excitement than fear.
Notice the imagery created in the opening words as well:
The sign on the wall seemed to quaver under a film of sliding warm water. Eckels felt his eyelids blink over his stare, and the sign burned in this momentary darkness.
The use of words like “quaver” and the comparison to “sliding warm water” are intriguing and create a sense of the unreal, and the sign “burned” in the darkness.
As the story continues, the pictures get darker both in color and content. There is dialogue, and they correspond with the darkening tone of the text as we find out that things could go terribly wrong if they affect anything else in the past other than the dinosaur they are supposed to kill.
Even though Eckels asks if it is guaranteed he’d survive, or if they are trying to scare him, he still signs up and the tone is excitement and curiosity.
As the pictures get darker in content and color, the choice of words does too. When Eckels kills his monster, he leaves the path. Travis gets angry at him and make him reach inside the dinosaur to pull out the bullets because they can’t be left behind.
The final picture and dialogue correspond to these lines:
“Okay, Eckels, get out. Don’t ever come back.” Eckels could not move.
“You heard me,” said Travis. “What’re you staring at?”
This is when we find out the by stepping on a butterfly, Eckles has changed history. The tone is didactic at this point. You don’t want to mess with the past. In the real world, it’s the law of unintended consequences.
The first link contains the text and original illustrations.