Use shorthand class .bg-repeat, .bg-no-repeat, .bg-repeat-x, .bg-repeat-y
<!-- .bg-repeat -->
<div class="bg-gray-lighter bg-c bg-repeat" style="background-image:url(bg.jpg);"></div>
<!-- .bg-no-repeat -->
<div class="bg-gray-lighter bg-c bg-no-repeat" style="background-image:url(bg.jpg);"></div>
<!-- .bg-repeat-x -->
<div class="bg-gray-lighter bg-c bg-repeat-x" style="background-image:url(bg.jpg);"></div>
<!-- .bg-repeat-y -->
<div class="bg-gray-lighter bg-c bg-repeat-y" style="background-image:url(bg.jpg);"></div>.bg-repeat
.bg-no-repeat
.bg-repeat-x
.bg-repeat-y