I've configured the United Nations Office for the Coordination of Humanitarian affairs (OCHA) icons into the stemapp, for use with draw tools. These icons are internationally agreed icons for humanitarian/emergency response, so should be a useful addition to the standard icons.
For more info on the OCHA icons: OCHA launches 500 free humanitarian symbols | OCHA
To add the icons,
1. Download and unzip the attached SymbolsInfo zipped folder, extract it and replace the folder at the following location \\arcgis-web-appbuilder-1.2\client\stemapp\jimu.js\dijit\SymbolsInfo .
2. Replace \\arcgis-web-appbuilder-1.2\client\stemapp\jimu.js\dijit\templates\SymbolChooser.html, with the attached SymbolChooser.html.
The symbols should now be available in the stemapp and any subsequent apps.
To do it restropectively (for apps already built), the SymbolsInfo folder is located at [app number]\jimu.js\dijit\SymbolsInfo and the SymbolChooser.html is located at [app number]\jimu.js\dijit\templates\SymbolChooser.html.
It should work with all the available draw tools that use this dijit.
Thanks to Stan McShinsky for his post on adding custom icons!