So, I’m discovering a number of things that IE8 doesn’t do that are “upgradeable” via javascript. I’m installing the js via a conditional so that I’m not loading it unless necessary.
Make it play nice with responsive design (bootstra) media queries: https://github.com/scottjehl/Respond
Make it understand cover/contain background images (logos): https://github.com/louisremi/jquery.backgroundSize.js (deprecated) or https://github.com/louisremi/background-size-polyfill
Of course, Modernizr.