Projects without image geolocation that are processed on the cloud will be in an arbitrary coordinate system and thus will not have a map on the background.
Projects with image geolocation will have as output coordinate system the same as the one defined by the image geolocation. If the image geolocation is in a geographic coordinate system, the output coordinate system will be the corresponding projected coordinate system in UTM zone.
If a project is uploaded from Pix4D desktop application, then the output coordinate system will be the one selected in Pix4D desktop app.