You can still work with img-responsive without impacting other images with this style class.
You can precede this tag with the section id/ div id/class to define a order within which this img is nested. This custom img-responsive will work only in that area.
Suppose you have a HTML area defined as:
<section id="work">
<div class="container">
<div class="row">
<img class="img-responsive" src="some_image.jpg">
</div>
</div>
</section>
Then, your CSS can be:
section#work .img-responsive{
margin: 0 auto;
}
Note: This answer is in relation to the potential impact of altering img-responsive as a whole. Of course, center-block is the simplest solution.