Many of them look very much like a dinosaur of some type. What do you think (in your opinion) was the origin of these types of images?
Who knows. Possibly imagination, possibly stylized renderings of something else, possibly nothing in particular.. whim. I'd be suprised if after examining thousands upon thousands of these ancient images, we wouldn't find any images that would partially resemble something like a dinosaur. If you look through the same set of pictues, you'll probably find some that look like airplanes, computers, figher jets, etc. from a certain angle or perspective.
There's nothing unusual about this. There is only so many ways of drawing quadrapedal animals, and a few of them, especially the abstract or the poorly rendered ones, are going to inevitably look like dinosaurs occasionally.
I can tell you with great certainty that there has never been any dinosaur fossils found that do not show great antiquity, and are not buried in the Cretaceous, Jurassic, or Triassic layers in the geologic strata. That means that dinosaurs have never been found anywhere near modern animal life, only with other dinosaurs and fossils of small primitive mammals that lived during that period.
