is this texture made up from procedurals? if it is then it is very difficult to get an accurate representation of skin this way.

the best way is to go into photoshop and create one there, use a photo to help obtain the colour skin tones and as reference to designing the texture.

3d Total Textures has a cd dedicated to just humans and creatures and has a library with plenty of skins, eyes etc to use.

Also maya software will only push those skin tones out to a certain extent, for best results use Mental Ray or if you have access then prehaps Renderman.