If I understand you correctly, you can do eye makeup by loading the head texture map in your 2d program, make two additional layers and white out the areas where you want the shadows to go in the third layer.  In the layer just above the base layer, fill it with black and save everything as a .jpg (should be a black background with your whites) then import it into your color_diffuse channel of your posersurface, the make a blender node and attach your .jpg to the blending channel.  The in the second channel, adjust the color to what you want  and adjust the blending channel dial to taste.  Should work for eye shadows as well as eye makeup.  Jan