Add image to model the example of Spree taxon model

add_background_to_spree_taxon.rb

class AddBackgroundToSpreeTaxons < ActiveRecord::Migration
  def change
    add_column :spree_taxons, :background_file_name, :string
    add_column :spree_taxons, :background_content_type, :string
    add_column :spree_taxons, :background_file_size, :integer
    add_column :spree_taxons, :background_updated_at, :timestamp
  end
end

taxon_decorator.rb

Spree::Taxon.class_eval do
  has_attached_file :background,
    styles: { large: '300x300>' },
    default_style: :large,
    url: '/spree/taxons/:id/:style/:basename.:extension',
    path: ':rails_root/public/spree/taxons/:id/:style/:basename.:extension',
    default_url: 'default_taxon_background.png'
end