Almost anything you could want from a GAN coloring book generator can be found on Google/DDG image search with "coloring page $NOUN". I mean, you can find almost anything that way: https://duckduckgo.com/?q=hacker+coloring+page&t=ha&ia=image... https://duckduckgo.com/?q=slug+coloring+page&t=ha&iar=images... https://duckduckgo.com/?q=bed+coloring+page&t=ha&iar=images&... https://duckduckgo.com/?q=teleport+coloring+page&t=ha&iar=im...

To save parsing the links, that's "hacker", "slug", "bed", and "teleport", all of which have perfectly reasonable hits.

I literally can't think of a halfway plausible coloring page that isn't covered that way. (Kinda thought I'd win that on "teleport", but... yeah, nope. Slim pickings at one result, sure, but that's still one reasonable result!)

Of course, you're pretty much writing off copyright laws in the process. How much that bothers you is up to you.