This is Keef's Skin Tester
I just wanted it in my own inventory. It's an ingenious way of testing skins, especially the seams.

Instructions from Keef's Tutorial Webpage
http://pixelpusher.us/learn_texture_skin.html:

Quick Instructions
-derive for the gender you need.
-apply your textures in place of mine.
-use the model to preview how your skin looks make any edits needed.
-once happy close the editor and derive from a IMVU skin to submit.

How it Works!
The tester will load with two dummy avatars. I tried to pose them so you can see all the seams more easily.

One model is sporting the neck that is on the body texture (between legs), the other is sporting the neck on head texture. S/he also has her eyes closed so you can see your eye makeup in the closed position.

NOTE: It is important that you make your skin so BOTH neck areas look correct as these necks are interchangeable depending on the outfit the avatar is wearing.

Aside the head of the dummy on the right there are exposed mouthparts for seeing those areas normally impossible to see to make it easy to preview dental work, tongue piercing, etc.

Once you get your skin textures ready to test load the Skin Tester then just swap out the head and body textures as you normally would. Hit 'Apply Changes' and the models will change letting you proof your work.

You can also swap the eye texture and remove the brows by adding an all-black opacity there if needed.

When happy with the skin edits you will use the normal IMVU inc skin product to derive from to submit with.