Rails image_tag helper for when an image may or may not exist.

welcome_helper.rb

  def image_tag_or_default(image_name, options = {})
    if RailsApplicationName::Application.assets.find_asset("#{image_name}").nil?
      image_tag("default_category.png",options)
    else
      image_tag("#{image_name}",options)
    end
  end

Rails.application.engine_name.titleize can probably be substituted here.