Can't postion an image over another one

[types field="image-intro" height="350" align="center" resize="proportional" class="img-shadow-1 image-intro" alt="[wpv-post-title]" title="[wpv-post-title]"][/types]

[types field="flexifriendly" state="checked"]
<img class="mtTool overlayright" 
	 mtposition = "top"
	 mttitle="Flexi Friendly"
  mtcontent ="Les produits estampillés Flexi Friendly sont modifiables sans frais,<br>
avant et pendant le voyage, sous certaines conditions."  
  	 src="http://gt-motors.eu/AFAM/wp-content/uploads/2013/12/label_flexi.png">
[/types]

.overlayright {
 display: inline-block;
position: absolute;
top: 0px;
right: 150px;
height: 74px;
width: 100px;
z-index: 10; 
 }