I don't like idea 1. This just makes people lazy, and it makes it hard to compete with people who have a huge portfolio already that they can just use for every challenge.

Option 2 is the best. You must use recent pics. The picture must contain the meta data for the date (however if you really wanted to cheat, people could change the meta data.) It would help though.

You could make a rule people have to post a selfie of them at the scene where they are taking the picture holding a steemit logo with their user name on paper and post their edited photo.