is your folder structure correct?
ie, if your face is called duck
do you have a folder blockland\add-ons\face_duck
the face at blockland\add-ons\face_duck\duck.png (256x256 .png)
the thumbnail at blockland\add-ons\face_duck\thumbs\duck.png (64x64 .png)
do you have other face addons that work?