_form_carrier_wave_file.html.haml

.field{:class => field.name}
  = label_tag "#{field.abstract_model.to_param}_#{field.name}", field.label
  .input
    - if field.bindings[:object].send("#{field.name}_url")
      .row
        = link_to field.bindings[:object].send("#{field.name}_url")
        %br
        = form.check_box "remove_#{field.name}"
        = form.label "remove_#{field.name}", "Remove existing #{field.label.downcase}", :class => "inline"
    .row
      = form.file_field field.name, :class => "fileUploadField #{field.has_errors? ? "errorField" : nil}"
      = form.hidden_field "#{field.name}_cache"
  -if field.has_errors?
    %span.errorMessage= "#{field.label} #{field.errors.first}"
  %p.help= field.help

_form_carrier_wave_image.html.haml

.field{:class => field.name}
  = label_tag "#{field.abstract_model.to_param}_#{field.name}", field.label
  .input
    - image = field.bindings[:object].send(field.name)
    - if image.path # the most direct check of an assets existence I could see
      .row
        -# load a default 'version' if it exists. should really be set through rails_admin's DSL:
        - default_version = image.versions[:main]
        = image_tag default_version && default_version.url || image.url(:thumb) #notice theres a `thumb` version for the uploaded image
        %br
        = form.check_box "remove_#{field.name}"
        = form.label "remove_#{field.name}", "Remove existing #{field.label.downcase}", :class => "inline"
    .row
      = form.file_field field.name, :class => "fileUploadField #{field.has_errors? ? "errorField" : nil}"
      = form.hidden_field "#{field.name}_cache"
  -if field.has_errors?
    %span.errorMessage= "#{field.label} #{field.errors.first}"
  %p.help= field.help

rails_admin.rb

if defined?(::CarrierWave)
  module RailsAdmin::Config::Fields::Types
    # Field type that supports CarrierWave file uploads
    class CarrierWaveFile < RailsAdmin::Config::Fields::Types::FileUpload
      register_instance_option(:partial) do
        :form_carrier_wave_file
      end
    end
    # Field type that supports CarrierWave file uploads with image preview
    class CarrierWaveImage < CarrierWaveFile
      register_instance_option(:partial) do
        :form_carrier_wave_image
      end
    end
    # Register field type to the types registry
    register(:carrier_wave_file, CarrierWaveFile)
    register(:carrier_wave_image, CarrierWaveImage)
  end
  RailsAdmin::Config::Fields.register_factory do |parent, properties, fields|
    model = parent.abstract_model.model
    if model.kind_of?(CarrierWave::Mount) && model.uploaders.include?(properties[:name])
      type = properties[:name] =~ /image|picture|thumb/ ? :carrier_wave_image : :carrier_wave_file
      fields << RailsAdmin::Config::Fields::Types.load(type).new(parent, properties[:name], properties)
      true
    else
      false
    end
  end
end