Update
After clarification from OP, it seems that a complete rewrite is required. (The desired layout/effect is called sticky footer).
1. Solution
Remove any z-index css rules and rely on natural flowing/stacking of elements:
http://jsfiddle.net/ws9kpoe3/10/
.text {
  position: relative;
  height: 100%;
}
.monimage {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
}
.img-wrapper {
  position: absolute;
  bottom: 0;
  height: 0;
  padding-bottom: 53%;
  width: 33%;
  margin: 0;
}
.img2 {
  left: 33%;
}
.img3 {
  left: 66%;
}
.img-wrapper img {
  padding: 0;
  margin: 0;
  width: 100%;
}
<div class='img-wrapper img1'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<div class='img-wrapper img2'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<div class='img-wrapper img3'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<img src="http://94.23.46.98/img/FEUILLES_2.png" class="monimage"/>
<div class='text'>
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Rem dignissimos distinctio quasi necessitatibus quam expedita, error facere pariatur quas aut in explicabo voluptates recusandae, nemo rerum et enim est magni.
</div>
 
 
2. Solution
Add another z-index rule to the .text block:
http://jsfiddle.net/ws9kpoe3/11/
.text {
  position: relative;
  height: 100%;
  z-index: 101;
}
.monimage {
  position: absolute;
  bottom: 0;
  left: 0;
  width: 100%;
  z-index: 100;
}
.img-wrapper {
  position: absolute;
  bottom: 0;
  height: 0;
  padding-bottom: 53%;
  width: 33%;
  margin: 0;
  z-index: 10;
}
.img2 {
  left: 33%;
}
.img3 {
  left: 66%;
}
.img-wrapper img {
  padding: 0;
  margin: 0;
  width: 100%;
}
<div class='text'>
Lorem ipsum dolor sit amet, consectetur adipisicing elit. Rem dignissimos distinctio quasi necessitatibus quam expedita, error facere pariatur quas aut in explicabo voluptates recusandae, nemo rerum et enim est magni.
</div>
<div class='img-wrapper img1'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<div class='img-wrapper img2'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<div class='img-wrapper img3'>
  <img id='img1' src='https://dummyimage.com/600x400/000/fff.png'>
</div>
<img src="http://94.23.46.98/img/FEUILLES_2.png" class="monimage"/>