This could be done as an optional way to sort images, but if we wanted it to be the default sorting then it would get a little complicated with how it interacts with the front page. If a "recently posted" image gets its creation date set far in the past does it immediately disappear off the front page?
I've always wanted this information. Sometimes a picture can be very misleading without knowing when it was taken. And I am useless at guessing!
Sometimes there are pictures with comments being often such as "this image is over 3 years old" in a response that model's appearance is completely different than current one. The proposed solution is to include a non-required field which would show approximate date - at least year - of when the picture was taken. This would also allow sorting (with upload date serving as tiebreaker).
A default value would be upload date, If the pictures are taken from public instagrams etc it is often in matter of months at most. For recordings of competitions, the value is pretty substantial.
An obvious disadvantage might be the work from community needed to properly label everything in order to make searches reliable, the freeform tags are still obviously not finished over the whole gallery (and question is if they ever be), so we are not stuck in a state where this would be counterproductive.