Replace those start, restart and stop spans/buttons with font icons instead of using real images, isn't much, but changes like that can improve page loading speed, and it will look much nicer with 3D button effect.
Replace the existing code with this:
<a class="btn btn-success btn-xs" href="#" ><span class="icon8 brocco-icon-play white"></span> Start</a>
<a class="btn btn-danger btn-xs" href="#" ><span class="icon8 brocco-icon-stop white"></span> Stop</a>
<a class="btn btn-warning btn-xs" href="#" ><span class="icon8 brocco-icon-refresh white"></span> Restart</a>
If you prefer black colored icons, then just replace span white to black, it will change icon color to black.