According to the wiki in order to install accountsservice and get it up and running you do the following;

Install accountsservice package

Then the /var/lib/AccountsService folder is created and you must create two sub-folders. An icons folder and a users folder.

Then you create a file named as your username in the users folder and an icon named using your username in the icons folder.

After that the user icon should be set and you will be able to see it on the lightDM login screen.

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However, this is not enough. In order to allow accountsservice to work properly and display the user icon the file permissions for the following must be changed.

/var/lib/AccountsService/users/<username>
/var/lib/AccountsService/icons/<username>.png

In order to allow accountsservice to work properly I've found that i must run the following comman

# chmod 755 -R /var/lib/AccountsService

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Additional info:
* package version: 0.6.39-1

The default permissions after installing and following wiki instructions are:

The AccountsService folder permissions look like

drwxr-xr-x 4 root root 4096 Oct 26 18:42 AccountsService

The icons and users folder permissions show as:

drwxr-xr-x 2 root root 4096 Oct 26 18:42 icons
drwxr-xr-x 2 root root 4096 Oct 26 18:42 users

/var/lib/AccountsService/icons/steven.png file permissions show as:

-rw-r----- 1 root root 19899 Oct 26 18:42 /var/lib/AccountsService/icons/<username>.png

/var/lib/AccountsService/users/steven file permissions show as:

-rw-r--r-- 1 root root 108 Oct 26 18:42 /var/lib/AccountsService/users/<username>