Fade In / Fade Out background images without white background
AHH ! Finally ! I found a nice technique ! I'm using a double wrapper.
The problem in your code is a bit logical. You can't fadeOut and fadeIn at the same time a single wrapper.
So the idea is to create two wrapper and to switch between them back and forth. We have one wrapper called: "wrapper_top" that encapsulate the second wrapper called: "wrapper_bottom". And the magic was to put beside the second wrapper: your content.
Thus having the structure ready which is the following:
<div id='wrapper_top'>
<div id='content'>YOUR CONTENT</div>
<div id='wrapper_bottom'></div>
</div>
Then a bit of JS+CSS and voilà ! It will be dynamic with any amount of images !!!
Here is the implementation: http://jsbin.com/wisofeqetu/1/