You can do this by adding a div i.e. centerBlock. And give this property in CSS to center the image or any content. Here is the code:
<div class="container">
<div class="row">
<div class="col-sm-4 col-md-4 col-lg-4">
<div class="centerBlock">
<img class="img-responsive" src="img/some-image.png" title="This image needs to be centered">
</div>
</div>
<div class="col-sm-8 col-md-8 col-lg-8">
Some content not important at this moment
</div>
</div>
</div>
// CSS
.centerBlock {
display: table;
margin: auto;
}