I never thought of using a picture to cover an opening! I DO like the idea. Hopefully, Charlie's access opening isn't too high or just off of the floor. Your idea kinda has me remembering now that the next time I run some plumbing in a finished wall I should put the shutoffs at 'picture height'. (Hopefully the homeowner likes the idea too. I'll be sure you get the credit!)
Yea, having a picture of the wife hanging just off of the floor behind the couch, or something, probably won't go over too well ...