This may seem trivial, but I’ve spent a lot of time trying to change my lightdm avitar to my user image. I am normally an Arch/gdm user and I have had no problems like this. I have searched wikis and forum to no avail. It is no big thing, but if anyone has a suggestion and wants to help with this, it would be appreciated. I’m sure this problem is due to my lack of familiarity with Ubuntu.
I got it working on my Acer computer by just changing the image in “about” on system settings. It doesn’t work on the System 76, maybe it is a cache issue or maybe I changed a config file that I can’t locate.
What a timely post. This evening I have been working on adding LightDM configuration to Ubuntu MATE and one of the features is to set the default avatar. I will be back porting to Ubuntu MATE 14.04 and 14.10.