Noch is used here as a "modal particle"
German makes frequent use of these particles to reflect mood in colloquial, often spoken, registers. They are infamously difficult to translate, as grammatical mood isn't encoded in English in this way.
Literally translated, your example could be: "Here is yet a photo from the Family Festival." However, unless you're coming from dutchy Pennsylvania where we sometimes use this particle specifically, the "yet" doesn't lend the same semantic value as it does in German.
Think of it as a means to draw attention to the fact that you're transitioning from one idea to the other, as if to say, "We have been spending a lot of time with family, and we are enjoying it! (In fact,) here is (yet) a photo from the family festival." Without the words in parentheses, the transition between those thoughts is less "smooth," sozusagen.