An important issue in serious photography is whether it's valid to try something which has been done before, or possibly been 'done to death'. It's fairly obvious that it is impractical to eliminate entire categories of photography on the grounds that 'it's been seen before'. By this logic we'd eliminate all nudes, landscapes, portraits, architectural shots, flowers, and virtually every other topic, leaving us to photograph extraterrestrials (assuming they visit), and not a hell of a lot else.
OK, what if were a bit more specific - what if we were to photograph nudes with high key lighting - sorry done before. So does this mean we can never ever again shoot a nude with high key lighting? Harry Calaghan did this 50 years ago. Should we then criticize every photographer since who has used this type of lighting to photograph nudes.
I think that categorizing images is the problem here. We need to evaluate images for whether it adds something to our understanding of the world or creates a reaction in us, even if we are fairly educated about the history of photography. Should it do so, finding another image by a different photographer with similarities really doesn't matter.
Think of writing instead of photography. Shakespeare used pretty standard plots, situations and conflicts in writing his plays. He's famous not for his original plots, rather for his fleshing out characters and use of language.
Frankly, if the only thing to recommend one's images is that they are new, then I for one don't think that's good enough. In fact I will predict that they won't last or be remembered, except possibly in a history of photography.
I'd rather be known for taking a great photograph of Yosemite rather than for taking the first photograph.
Rather than spending your time pigeonholing an image, stop, look and enjoy it. If it happens to be very similar to another image you have previously seen and is even better, well isn't that wonderful. If it adds nothing to your experience, well don't bother looking at it again.
Which brings up an important point, photography isn't a contest (or at least it isn't most of the time and probably shouldn't ever be).