class MiqProvisionDecorator < MiqDecorator
  def self.fileicon
    '100/miq_request.png'
  end
end

class MiqProvisionDecorator < MiqDecorator
  def self.fonticon
    'pficon pficon-unknown'
  end
end

Replace miq_request.png with pficon-unknown in MiqProvisionDecorator
Replace miq_request.png with pficon-unknown in MiqProvisionDecorator
