If it's on Wikimedia Commons there's nothing grey about it - it's good to use. Another non-grey area is - if it's a photo that was taken under the jurisdiction of Japan before 1946, it's public domain, i.e. free for anyone to use for any purpose. And if something's passed into public domain it can't be re-copyrighted unless it's a derivative work that *significantly alters* the original.
I don't have a horse in this race, I'm perfectly fine with doing the linking thing, actually I prefer it over having a huge thread with 69 pics embedded each at 1 GB in size that makes the page take three days to load.... I just want everyone to be clear on the wiki stuff. If it's on Wikimedia Commons, it's fair game. If it's on Wikipedia and it's an image, 95% chance it's fair game. If it's on Wikipedia and it's text, it's fair game. You could, if you wanted, copy text from Wikipedia and publish it in a book, as-is, and try to sell it. But you wouldn't be able to claim copyright on a book like that.