followers_controller.rb

class FollowersController < ApplicationController
  before_action :authenticate!
  def index
    @pictures = current_user.followers.pictures
  end
end

picture.rb

class Picture < ActiveRecord::Base
  scope :filter do |type|
    case type
    when 'hot'
      where('some SQL mumbo jumbo')
    when 'recent'
      order('pictures.created_at DESC')
    end
  end
end

pictures_controller.rb

class PicturesController < ApplicationController
  before_action :authenticate!
  
  #If a user is a guess, it redirects here.
  def index
    @pictures = Picture.filter(params.fetch(:f, 'all'))
  end
end

routes.rb

YourApp.routes.draw do
  
  resources :pictures
  resources :followers
  
  root to: 'pictures#index'
end