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."
E.g.
照片在这儿了,你看着办吧。
照片在这儿了,不能退回去了。
Without 了, it's more natural if you have some additional information about retrieving the photos.
E.g.
照片在这儿,不过缺了一张。
照片在这儿,不过照片上没有她。
Or, when 这儿 is the key point, 了 is not needed.
照片在这儿,不在那儿。
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.