Are you looking to this on a server, or are you trying to customize the UI for your own project?
Servers can define how many characters a player can have using commands like setslots or Config.Slots . esx_multicharacter.rar
Higher-end versions focus on the "flow" between the loading screen, identity creation, and spawning into the world. Are you looking to this on a server,
Some versions allow server owners to set specific animation dictionaries so characters are performing actions (like waving) while the player selects them. esx_multicharacter.rar