1. A machine-implemented method, comprising: receiving an indication that a user is placing a graphical representation of a metadata-defined image on a design canvas using a graphical user interface; associating the graphical representation of the metadata-defined image with metadata defining the particular metadata-defined image, wherein the metadata specifies one or more properties associated with the metadata-defined image; exposing at least a particular property of the metadata-defined image to the user; and enabling the user to specify one or more conditions for that particular property, wherein the one or more conditions will be applied to adjust a value for that property during display of the metadata-defined image.