This photo is posted for the "merci" plaques on the right hand side. I believe they are for prayers that have been made in front of the statue and answered. It's an odd photo, because I don't have any photos of the plaques - except on the extremities where they have been caught while I was taking a photo of something else.
merci'Thank you', as I am sure most of you know. Most text books tell you that if you want to say 'thank you very much' it is merci beaucoup. There's nothing wrong with this, but I notice that in practice most people here say merci bien. I think this is slightly more casual and relaxed. If you really want to stress how very grateful you are when someone has done you a really good turn, knowing that the proper response is the quite formal je vous remercie goes down a treat. You can expect a modest smile (a combination of amusement at your accent and pleasure that you have acknowledged the good deed) and either de rien ('it's nothing') or je vous en prie ('you're welcome'), spoken in a super rapid fire mumble, as it is a polite but instinctive, formulaic rejoinder.
Merci is generally pronounced 'mare-see', but we notice that some people here say something that sounds more like 'mare-sheesh'.