has_profile.rb

# lib/media_library/models/has_profile.rb
module MediaLibrary
  module Models
    module HasProfile
      extend ActiveSupport::Concern
      
      # Define methods that get called on classes 
      # that include file
      module ClassMethods
        
        # method to call on the models that have are profileable
        # 
        # This can call any number of active record class methods
        # that are relevant to profileable.
        def has_profile
          has_one :profile, as: :profileable

          delegate :description,:title,:content_type, to: :profile

          accepts_nested_attributes_for :profile           
        end
        
      end
      
      # Empty for now be cause I can't think of any necessary methods
      # right now that is.
      module InstanceMethods
      end
    end
  end
end

# Include the module in all of ActiveRecord::Base since we need this in every model
ActiveRecord::Base.include(MediaLibrary::Models::Profileable)

# Once this is all done in your models you can now use
#
# app/models/media_library/image.rb
module MediaLibrary
  class Image < ActiveRecord::Base
    
    has_profile
    
    # … Omitted for awesomeness …
  end
end

# app/models/media_library/document.rb
module MediaLibrary
  class Document < ActiveRecord::Base
    
    has_profile
    
  end
end

Good articles on using ActiveSupport::Concern http://chris-schmitz.com/extending-activemodel-via-activesupportconcern/
and http://www.fakingfantastic.com/2010/09/20/concerning-yourself-with-active-support-concern/