In regards to the "no spines before 1993" claim, I found a few pre-1993 dinosaur illustrations that depict dorsal spines in dinosaurs that weren't/aren't believed to have them. For instance, like the picture, here's a triceratops with spines, on a stamp from the Republic of Guinea:
As you can see it has similar dorsal protrusions to the Ica stone picture.
Here's an iguanodon (I guess) with spines, from the same source:
So it's not inconcievable that the Ica stone hoaxers would have seen dino illustrations that had spines that paleontologists at the time didn't believe actually existed.