了 is to signify the completion of the statement.
With a 了, your tone is more completed and confirmed. It's like "The thing is done. Take it or leave it. / Deal with the rest."
Without 了, it's more natural if you have some additional information about retrieving the photos.
Or, when 这儿 is the key point, 了 is not needed.
The tone is not highly stressed, so it's just a general feeling. Whether to add or to omit 了 is not strict in above cases.