White Whytee is a bald white guy wearing a black leather coat with red outlines, a grey shirt, a pair of jeans and sunglasses. Based on his quote, it appears that he may be a biker.
White Whytee is only available in Serious Sam HD: The Second Encounter if the player has Serious Eight DLC. Otherwise, it is impossible to use him. Since it is currently impossible to get the Serious Eight DLC, those who don't already have it won't be able to use him at all.
White Whytee's model can be found in Serious Sam HD: The Second Encounter's files even without the Serious Eight DLC. This suggests that he was supposed to be in the game from the very beginning, but was cut for an unknown reason.
This model can be obtainable if you buy retail version of the game.