n both single-player and multiplayer roleplaying games, one of the first experiences is often choosing the appearance of your character. Even my Dungeons and Dragons character sheets provide limited ways to describe the look of a character, and many players go beyond this to find some sort of image that fits their mental ideal.
Choosing from a list of predefined models or pictures is the simplest means for character customization, offering the player basic input into how their character appears. Older RPGs, and even relatively recent games like the Knights of the Old Republic series, have utilized this technique.
Race or age? Skin color's easier to simulate than wrinkle are.A more complex system allows players to pick from various faces and hairstyles, though it does not allow for any differences in body type or age, and still limits selection to merely a combination of different faces and styles.
Even more advanced customization options tend to focus on the face, with sliding-scale proportions for different features, various eyes, and tattoos and piercings being more common than varying body types or age options. Changes in skin color are easier to implement than, say, simulating wrinkles.
Given that the avatar's head is often used for various menus, and may be focused on in cutscenes and other aspects of the game, additional detail for this area makes sense. One older example is this cut scene from the first Knights of the Old Republic (warning: spoiler). Another is Mass Effect. And zooming in on the faces of non-player characters during conversation is also quite common, used in Bethesda titles Oblivion and Fallout 3.
One size doesn't fit all. Musclebound mage? Spindly warrior?While I will admit to having spent quite a bit of time tweaking a character's face, even after achieving exactly what I'm after, the avatar can be quite disconcerting if there is a lack of choice between body types. Both the magic-wielding mage who sports the muscles of a bodybuilder and the plate-wearing, sword-swinging woman who looks liable to fall over provide quite the disconnect. But making sure armor and clothing fit on more bodies also requires extra time and effort.
Given the increased graphics quality of current games, I hope to see even more opportunities for different facial and body options with characters. And, also, given that some more detailed creation options can still fail to meet aesthetic standards, that the design of these would look pleasing as well as detailed.

Ahhh, character customization. It is incredible how massive the array of possibilities can be.....for somebody who knows what they are doing. But when it gets to the point where you can adjust a person's nose and lips.... I usually don't have a preference there and can hardly tell the difference (unless I max out the scroll bar in either direction).

Chris and I, as a rule, always create the most hideous characters possible.
Otherwise we would spend far too long trying to make characters with our likeness -- and we all know that digital versions of ourselves never look right as it is.
With one of my fascinations being physical anthropology, and my opinion of character customization tepid, I have a long-marinating notion to oversee the making of middleware that accounts for dozens of facial and body types that are easily recognized around us but are rarely found in the square-jawed, button-nosed presets of character-creation.