Decide first on what model you are going to use, because the two you mentioned both have different texture maps.

The picture you posted should be fine. The eyes will be on their own texture map, and the eyebrows will go on the main face/head map. Download SnowSultan's UV maps from his freestuff area here: http://www.renderosity.com/mod/freestuff/index.php?user_id=856

Basically, start by copying and pasting the pictures you want to use over the UV map in Photoshop, and use a soft eraser to get rid of the edges so they blend together smoothly. You'll probably need to use the transform tools as well to scale or rotate the bits you want as well.