"Pretty" in particular is a word that gives me a lot of trouble - I've never actually been able to pin down a coherent, consistent meaning for it. Assuming that you're trying to get at a message of "the only interesting aspect of this picture is its aesthetics", though, I suspect that I would indeed find it objectionable, particularly if the picture itself was also edited to remove any bits that might be interesting for other reasons or to put focus on some particular aesthetic aspect at the expense of allowing other interpretations. (I'm more of a visual thinker than a textual one, so I find the composition of pictures to be more relevant than the captions, which I often don't even read. Some people are the opposite, so both are important in general.)