1. Text content search with keywords/sentences or people's names. This is the best way, but finding good keywords is hard. 2. Randomly browsing, especially typography trade journals. Internet Archive has all issues of Inland Printer for example. Reading through them I've found many new pictures and keywords to do further searches on.
However, there's some arabic letterpress stuff in the archive! https://garden-of-flowers.heikkilotvonen.com/?filters=arabic I hope to find more, especially the kufic style, but I haven't found many good sources for that kind of stuff yet.
Wow this is awesome, they had box-drawing characters in 1785!
—Fun with your typewriter by Madge Roemer https://archive.org/details/FunWithTypewriter/mode/thumb
—Artyping by Julius Nelson https://archive.org/details/Artyping-HQ/mode/thumb
—Typewriter Art by Alan Riddell https://archive.org/details/TypewriterArt-AlanRiddell/mode/t...
I’ve been variously told it looks like the sun, a hedgehog, and a lion & I’m kind fond of all those descriptions