Issue with player icons

First of all, please forgive me if there is some language errors in the following text, I am french.

Since the first time I launched this game I didn’t understand how the player icons are working.
A few icons are avilaible from the begenning, some of them must be unlocked during events and some of them must be unlocked by doing some ations for exemple by playing a certain number of games.

The thing that I don’t undersatnd is what kind of games I must win to aquire the icons.
With time, I finally aquired some specific icons like the Throwing Axe Man or the Cataphract. I don’t play multiplayer games so I supposed that these icons only, could be aquired by playing singleplayer games. But recently, I don’t know how, all of these icons desapeared from the list of unlocked icons, exept the icons which I had unlocked during events and the basic icons.

So now, I don’t know anymore how the player icons system is working.
Must I win games only in multiplayer or the singleplayer games are working for some kind of icons? Why the icons that I won desepeared? And why the icon that I selected didn’t desepeared despite it has desepeared from the unlocked icons?

Please explain me if you can, how all of this is working.
Thank you in advance.