Hashtags are increasingly used to promote, foster and group conversations around specific topics. For example, the entertainment industry widely uses hashtags to increase interest around their products. In this paper, we analyze whether hashtags are effective in a niche scenario like the art exhibitions. The obtained results show very different behaviors and confused strategies: from museums that do not consider hashtags at all, to museums that create official hastags, but hardly mention them; from museums that create multiple hashtags for the same exhibition, to those that are very confused about hashtag usage. Furthermore, we discovered an interesting case, where a smart usage of hashtags stimulated the interest around art. Finally, we highlight few practical guidelines with behaviors to follow and to avoid; the guidelines might help promoting art exhibitions