Here are some shots of the boxes I've finished since my last post:
Anya guessed the idiom! That ghostly subtitle at the bottom reads: "The Tale of a Dubious Friendship." It opens up to this:
This next one is super tiny:
And the idiom is harder to guess. But can you? I'll give you a hint: what is the malevolent-looking girl on the left doing? The word "gesture" in the title is also helpful.