A question for Mini-Spotlight users/experts

[alex526]

We are revamping the que area in our haunt. We have a rectangular area (35x20). I am styrofoaming the walls to look like castle walls. Give or take 1 or 2, how many mini-spots do you think I will need to give all the proper attention to the detail, but still keep it more dark than lit up? I welcome any and all suggestions.