Just to add on to he information Lord has provided you, when nameing a file for a bi-color eye to not name the additional file after any low numbers such as
preset_5eye.jpg
or
preset_12eye.jpg
Cause if you add any range of number from 1-12, then it will use the original file name that is stored in that folder
usually it helps out better to just name the eye after the file and at the end add "R" and "L" to the files