I'd look at the Documentation for the Bootstrap 3 grid and really work through some of the examples to make sure you understand that.
Here is a runnable snippet of your current markup:
<!-- begin snippet: js hide: false console: false babel: false -->
<!-- language: lang-html -->
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<div class="container-fluid">
<div class="row-fluid">
<ul>
<li class="span4"><img src="https://picsum.photos/200/200?image=1" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=2" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=3" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=4" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=5" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=6" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=7" alt=""/></li>
<li class="span4"><img src="https://picsum.photos/200/200?image=8" alt=""/></li>
</ul>
</div>
</div>
<!-- end snippet -->
If you just want each of the images to take up 4 out of 12 columns at all screen sizes you can use .col-xs-4
, but without more info as to what you're expecting to achieve, it would be hard to say for sure what you need to do.
<!-- begin snippet: js hide: false console: false babel: false -->
<!-- language: lang-html -->
<link href="https://cdnjs.cloudflare.com/ajax/libs/twitter-bootstrap/3.3.7/css/bootstrap.min.css" rel="stylesheet"/>
<div class="container">
<div class="row">
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=1" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=2" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=3" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=4" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=5" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=6" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=7" alt=""/></div>
<div class="col-xs-4"><img src="https://picsum.photos/200/200?image=8" alt=""/></div>
</div>
</div>
<!-- end snippet -->