I think the only way is to hire a contract killer :) All of your pics are visible to anyone anyway (also outside 365...), so deleting a follower wouldn't really change anything except that the follower wouldn't get notifications of your new pics in his/her newsfeed.
@pocketmouse@newbie had to share as it made me laugh. I thought pocketmouse was telling newbie that the follower to be deleted was scrivna! Out of interest does he ever post photos?
Yeah he does :) http://365project.org/Scrivna/365