AddThis Pinterest has support for "at_include" and "at_exclude" classes for images.
Full post here: http://support.addthis.com/customer/portal/articles/1300322-pinterest-image-sharing#.UuAnmrvTm2x
Include Images
You can instruct the share preview to only grab specific images from
the page by using the “image_include” configuration option. First, set
image_include to your desired class name (id selectors are not
allowed, only class selectors), then add that same class name to each
of the images on the page that should be grabbed. For image_include,
don’t add the ‘.’ selector. Here’s an example:
<script type="text/javascript">
var addthis_config = {
image_include: "at_include"
}
Once image_include has been defined with a class, add that class to
the desired images on the page. In this example, the only images on
the page that will be grabbed, will be the images with the at_include
class (img1.jpg and img3.jpg).
<img src="http://www.example.com/img1.jpg" class="at_include" />
<img src="http://www.example.com/img2.jpg" />
<img src="http://www.example.com/img3.jpg" class="at_include" />
Exclude Images
You can instruct the share preview to ignore specific images from the
page by using the image_exclude configuration option. First, set
image_exclude to your desired class name (id selectors are not
allowed, only class selectors), then add that same class name to each
of the images on the page that should be ignored. For image_exclude,
don’t add the ‘.’ selector. Here’s an example:
<script type="text/javascript">
var addthis_config = {
image_exclude: "at_exclude"
}
Once image_exclude has been defined with a class, add that class to
the desired images on the page. In this example, the only image on the
page that will be grabbed, will be the image that doesn't have the
at_exclude class (img2.jpg).
<img src="http://www.example.com/img1.jpg" class="at_exclude" />
<img src="http://www.example.com/img2.jpg" />
<img src="http://www.example.com/img3.jpg" class="at_exclude" />
Image Container
You can also instruct the share preview to grab images from a specific
container, such as all the images contained within the class or id
that has a Pinterest share button. This can be really helpful if there
are multiple Pinterest share buttons on the page. Remember, the
Pinterest share button must be within the same container that the
images are located in. Also, notice that image_container needs to have
the ‘.’ or ‘#’ selector. Here's an example:
<script type="text/javascript">
var addthis_config = {
image_container: ".shared_content"
}
Once image_container has been defined with a class, add that class to
the desired on the page. In this example, the only images on the
page that will be grabbed, will be the images contained within the
shared_content .
<div class="shared_content">
Here's some example text. Images in this div will be grabbed.
<img src="http://www.example.com/img1.jpg" />
<img src="http://www.example.com/img2.jpg" />
<a class="addthis_button_pinterest_share"></a>
</div>
<div class="another_div">
Here's some more example text. Images in this div will not be grabbed.
<img src="http://www.example.com/img3.jpg" />
<img src="http://www.example.com/img4.jpg" />
</div>