The ability to add a service is very nice but limited due to the iFrame. Also the iFrame only fills about half of the available space. It should use 100% height to fill all available space.
The services would benefit greatly from using an HTML page instead. When creating a new service it would ask if you would like to use an iFrame, options same as now, or upload an HTML file. For advanced users, we could sftp to the server, locate a folder representing that service, then add some more files, e.g. JS, CSS, and/or PHP to make it even nicer. The REST API could be the perfect glue to make it come together.
The home page already kind of works like this except it is pr project and only publicly viewable. With a build your own service the community could even share useful plugins with eachother.