I think there is a miscommunication going on with language-usage here. In English, when Nats used the phrase "It is a shame that . . . " he was using a common English phrase that simply means "I wish it were otherwise". In English you can sometimes drop the "It is a . . . " part of the sentence above as "implied" and still be understood by simply saying "[It is a] ... Shame that . . . ". The phrase does not imply any type of shame as it is often used in Asian culture.
He was not saying or implying that there was any type of shame involved in anything that you did, or that there was anything shameful in your work. He was merely expressing the wish that there was a version of your picture that did not have the logo and title in the corner.