score:6
Your best bet would be to visit shrines during a festival such as Setsubun or New Year's day. These will usually include some public ceremonies, rituals or performances in which the Miko participate (Kagura dance is mentioned in your Wikipedia excerpt), and these are public events with many people attending and taking photos.
Upvote:8
Less formally, mikos are simply employees of the shrine (it's a very popular baito option with college girls, since the pay is relatively good, the job is not tiring, and you get to wear a nice costume), when there is not a festival they perform various tasks around the shrine like cleaning or attending the souvenir shop. Just go to your local shrine, anywhere in Japan, and you will find them. Taking pictures is certainly OK, and they don't mind a little chat either if they are not too busy (and you can speak Japanese). I took this at the Hachiman-gu shrine in Morioka: