Dragonfly images in a polymorphic association syntax?

I have a pictures model:

class Picture < ActiveRecord::Base
  belongs_to :imageable, polymorphic: true
  dragonfly_accessor :image
end

And then I have two different models that should be able to have pictures:

class Teacher < User 
  has_many :pictures, as: :imageable  
end

class Student < User 
  has_many :pictures, as: :imageable
end

I followed instruction here to setup dragonfly and had it working when I just had one model with an image attribute but now that I want to make its own picture model that other models can have_many of then it stops working: http://ift.tt/1P4iXd3

In my rails console I can do something like:

teacher = Teacher.last
teacher.pictures 

and get returned an empty active record proxy:

#<ActiveRecord::Associations::CollectionProxy []>

but I cannot do:

teacher = Teacher.last
teacher.image
teacher.picture.image
teacher.pictures.image

When I try to display on my show view:

<%= image_tag @teacher.pictures.thumb('400x200#').url if @teacher.pictures_stored? %>

I get

undefined method `pictures_stored?'

Even if I delete the if @scientist.pictures_stored? I then get this error: undefined method thumb'

I have tried different combinations since dragonfly gives us the dragonfly_accessor :image on our pictures model. But not sure how to actually reference it. Any help is appreciated.

via Chebli Mohamed