When it came to unusual things, Castiel had a number of them to show her, though he was willing to save it for the time being. The other planets in the solar system, the minds of cats. Perhaps even the Heaven he often took refuge in, though he was careful about that. It was one of the few places in Creation he'd ever felt at ease. It'd not been his own - angels were not issued their own versions of Heaven, but...it was quiet. Few angels sought him out there. And despite his centuries, Cas still felt as though it were one of the truly safe places. Even if that likely wasn't true anymore.
As for why he'd shared it with her...he didn't know. Perhaps it was because Helena too sought some form of peace. It wasn't something he was looking to question. And to him, she was special. There had been no need for her to be kind to him, yet she'd accepted him. Without skepticism or question. To Castiel, that meant a lot.
As for the paper animals...he wasn't terribly good at it, but he tried. Perhaps in the future he would improve. For her, he was willing to practice.