There's a slight trick to it.

You use hider2 for the imbedded one. Use the view raw to see what I mean.
[hider=Test Hider 1]
Random Gibberish. Lorem Ipsum...

[img]http://www.iiacanadanationalconference.com/wp-content/uploads/2013/01/test.jpg[/img]

[hider2=Test Hider 2][img]http://www.iiacanadanationalconference.com/wp-content/uploads/2013/01/test.jpg[/img][/hider2]

gbrftlosuijefiudjewuif (gibberish)
[/hider]