Imposter Syndrome Is Not a Delusion
The feeling says you are not who you appear to be. Before you correct it, check whether it is false. You chose the photograph yourself, and you know which frames you discarded.
Imposter syndrome is usually described as a cognitive distortion. You are competent, you feel like a fraud, the feeling does not match the facts, and the work is to correct the feeling. Believe in yourself. You earned your place. Everybody feels this way.
I think that advice is wrong, and wrong in a specific direction that makes the problem worse. The feeling is not a distortion. It is an accurate reading of something real, and telling a person to override an accurate perception is not therapy. It is gaslighting with good intentions.
Start with what the feeling actually reports. It does not say I am incompetent. Competent people have it most, which is the detail every treatment of the subject notices and then walks past. What it says is narrower and stranger: I am not who I appear to be, and one day this will come out.
Now ask whether that is false.