Rob: My way of working is this. If I like an image and don't have any suggestions to 'improve' it, I'll simply say so. If I like or don't like an image but have an opinion about how it might be changed, I'll add that. If an image doesn't do anything for me and I don't have any suggestions, I simply don't say anything. Just because I don't like it doesn't mean that everyone else has to dislike it too!