The image loader prefix is 'wadouri' (note that the prefix dicomweb is also supported but is deprecated and will eventually be removed). Here are some example imageId's:
absolute url:
wadouri:http://cornerstonetech.org/images/ClearCanvas/USEcho/IM00001
relative url:
wadouri:/images/ClearCanvas/USEcho/IM00001
WADO-URI url:
wadouri:http://localhost:3333/wado?requestType=WADO&studyUID=1.3.6.1.4.1.25403.166563008443.5076.20120418075541.1&seriesUID=1.3.6.1.4.1.25403.166563008443.5076.20120418075541.2&objectUID=1.3.6.1.4.1.25403.166563008443.5076.20120418075557.1&contentType=application%2Fdicom&transferSyntax=1.2.840.10008.1.2.1
Orthanc file endpoint URL:
wadouri:http://localhost:8042/instances/8cce70aa-576ad738-b76cb63f-caedb3c7-2b213aae/file
Note that the web server must support Cross origin resource sharing or the image will fail to load. If you are unable to get CORS enabled on the web server that you are loading DICOM P10 instances from, you can use a reverse proxy. Here is a simple Node.js based http-proxy that adds CORS headers that you might find useful.