A fellow classmate blogged about indexing with limited information recently. I too have been debating the best approach to handling this as I make my way through indexing the images.
For example, one of the DePol images is clearly (to me) a Biblical illustration. A hint that this is the case is in the title of the image just before it: Fisherman of Galilee. I went ahead and assigned subject content values (title, subject terms, etc.) even though I do not have any provided information to go on. I wonder if this is interjecting too much. Otherwise the content description would be so vague, it wouldn’t be very useful.
I also considered trying to add temporal coverage of Biblical times, but here my uncertainty was too great. Decided better to leave blank than enter something erroneously.