Well, Source was the last Counter Strike game that allowed people to use custom skins. CS2 enforces sv_pure when playing on official servers, so you can't make up your own skin and use it. It sucks.
At one time[1] Valve even tried to ban community servers that offer custom models/skins. Though they doesn't seem to enforce it anymore.
[1]: https://blog.counter-strike.net/index.php/server_guidelines/