Hi,
this is my first Post on Discuss, hi Peoples 
like you are know have i build up KristalSVG Icontheme (search easy “blacky”)
i noticed nobody did not know where have to put the Usericons . In Programs so apps, Emblems or what…
This “problem” it exist since year 2000 and the whole 24 years now… so, why not make easy in the Icontheme a extra category for all the nice User-Pictures with name user-01/100000 and user123 and so on … therewith it’s also possible for the user at the actual theme for upload his Usericon in $HOME or select via pulldown out from
$HOME /.local/share/icons/$Themedir/scalable/users
than have we a folder where need not need to be in the Iconselector, but then it is open via User Manager , pulldown selector, and if the user have an Userpicture, need he only put the picture in this ~/users folder and this folder can be in the Category “Users” … or even in the actual theme ~/users folder
and all User pictures can kicked in in this folder ~/users folder and the apps folder it’s a bit more cleaned up.
And the Themecreators and Themecompilors can all collected User-Pictures
put even in this ~/users folders or throw 
best regards
Blacky