http://imageshowhide.mozdev.org/
I havent used it, so i dont know if it replaces images with alt text, but it will hide images. I always look at sites i build with lynx to see if it can be navigated with lynx. someone told me about links (after i made a smart ass comment about them spelling lynx wrong). I found out its actually eLinks but it comes installed on FC2 and is also a CLI browser.