By nature images are not responsive. If you want Images to be Responsive just add class "size-auto" to them and they will re-size to the screen size. We have example of images with Lightbox on them that work with responsive design.
<img class="size-auto" src="/image" alt="Sample Image"/>
Image Styles
border
polaroid
well
round
<img class="size-auto polaroid" src="/Image" alt="Sample Image"/>