The one issue with creating responsive web design is in displaying images, especially getting the most appropriate size in a particular screen size. One solution for it is the Responsive-Enhance jQuery plugin. It works by loading small-sized images by default, then checks the screen size and loads the bigger version if necessary.
According to its creator, Josh Emerson:
This results in a faster perceived page load speed, but a slower actual speed. I’m happy with this solution as I care more about perceived speed than actual speed.
This tutorial by Keir Whitaker takes the whole thing further by teaching us how to apply Responsive-Enhance in WordPress.