Our official client has six player sprites built-in; but only the first two (default male and default female) are usable by general players due to lack of support for customisation at this time. However, certain Staff members are able to use one of these four different sprites to be distinctive and easily noticeable in-game - these tend to be Staff who have good reason to be in the public eye or high-ranking Staff; and typically they take the appearance of Lance but there are some exceptions. For example, I myself use a Team Rocket male (although this is just on your end - I actually have a custom Gengar sprite in my own skins, but it's not been distributed publicly because it's Carel's work and I would not wish to see her work stolen for other people's personal use), as does at least one other Staff member.
It's not currently possible for players to set different sprites for themselves, except by changing the sprites in folders 1 or 2 in their current skin (which will change all male or all female player's sprites to the same as yours). We are looking into actual customisation possibilities for the future, however we think there are better solutions to what Shane planned; which we hope to look into when we are further into development of a new client for the game. There once was a time where Shane gave certain players Lance sprites; however this was against policy and those players were subsequently changed back to their original look.