Writing to Disk using Raspberry Pi image

I understand that Channels DVR Server for Raspberry Pi uses a read-only file system. But I also know that certain paths are writable. I would like to make extensive use of Docker using the image but I need paths in which I can store configs and working files. I know I can use media, but is there a list of other writeable paths I can use for this purpose?

The only writable directory is /mnt/data. It is space limited and holds all the channels dvr software and docker images.