An appliance development toolkit includes access to user interface domain data, an editor configured to create one or more instances of user interface control data, to create a map for associating the instances with one or more resource identifiers, and to create a map for associating one or more theme identifiers with the resource identifiers. The toolkit also has a converter for creating content based on the instances of user interface control data and the maps. The content is in a builder file. An appliance, having a graphical user interface with which a user can control and observe operation of the appliance, can use the builder file at runtime to dynamically render its graphical user interface based on resources in response to selection of a theme.