I'd prefer the 10 percent that spends more than twenty seconds looking at it and understands it.
Do you truly PREFER that? Or are you just willing to accept it?
Would the photo lose something if you were to reformat the same message to be understood by 75% of people instead?
It might lose something (a secret decoder ring is no fun if anybody has one, etc. etc.), but just wanna sort of push you to ask yourself whether that really is the case here.
You mentioned museums for example, early on, which implies more of a popular understanding, not niche. For example, most Pullitzer prize photos are very obvious and forceful in their message by comparison, like this one:
http://worldsfamousphotos.com/wp-content/uploads/2007/04/spot_news_-1.jpg
You almost get the message before you even register what the content is.