refinery/refinerycms-page-images — pull request #96 by givanse (2013-12-19 15:13:09+00:00)
Title: Use a Hash instead of a String for image.thumbnail()

This is necessary or you'll encounter this error:
can't convert String into Hash

The possible options for image.thumbnail() are:
options = { :geometry, :strip }

Source: https://github.com/refinery/refinerycms/blob/master/images/app/models/refinery/image.rb#L40