Edit images inserted by CKEditor.

Hi, I use CKEditor for ASP. NET with Enhanced Image in my site. When I insert Image I get code which Isn't good to me. I would like to replace some tags. I tried to replace tags using String.Replace, String.IndexOf etc. methods, but it does not make sens. I would like to try modify sourde code of CKEditor in order to achieve my goal. When I use simple picture, without signature/description, I get code like this (float depends of selected option):

<p>
<img width="481" height="361" style="float:right" src="/Images/ev1.jpg" alt="">
</p>

I'd like to convert it to this:

<a data-lightbox="gallery" href="/Images/ev1.jpg" class="image-container span4" style="float:right;margin:5px">
	<img class="shadow" style="margin:5px" src="/Images/ev1.jpg">
</a>

Another result is when I use image description. I get this code:
 

<figure class="image" style="float:left">
<img width="579" height="445" src="/Images/ev2.jpg" alt="">
<figcaption>This is picture description</figcaption>
</figure>

Which should look like this:
 

<a data-lightbox="postPhoto" href="/Images/ev2.jpg" class="image-container span4" style="float:left;margin:5px">
   <img width="579" height="445" src="/Images/ev2.jpg" alt="">
   <div class="overlay">This is picture description</div>
</a>

Could you, please, help me to solve my problem?