A few years ago (in fact, ten! years ago) I wrote here a about a simple trick that allows you to get a photo out of a Pages document. It's not obvious but quite easy once you know it; and useful because you are probably more likely to remember a Pages document where you used a photo rather than where and under what name the photo is filed and stored.
Once again, in the current version of Pages:
— click on the photo to select it in a Pages document;
— in the Inspector panel click on 'Image';
— click and hold on the photo file icon and drag it to Desktop;
— now you can put it into Photos, send as an attachment, change the file name or use for whatever purposes you'd been looking for it.