David Scotson

Have you tried copying/moving the afterburner pix folders into your theme to see if thy continue to work?

Might show up issues like minor naming problems, or file permission issues.

So, for the gif issue, I'd suggest not creating any .gif files, so that when it finds your new PNG files, it'll use those instead. Then there's no need to mess with the code. (Also, does 2.3 support SVG?, I know the icons were overhauled in 2.4 but I'm not sure when support for the SVG format was added).

Which takes us back to why it's not picking up your new PNG images. It's not clear to me why you would be having trouble. My best guess is that you're not putting the new files in the right place.

Have you followed this guide? (and the note right at the top which suggests being in "theme designer mode" while making changes so that you can the difference instantly? Remember to turn it off when you're done):

http://docs.moodle.org/dev/Using_images_in_a_theme#Overriding_images_in_your_theme

As far as I'm aware Font Awesome should work with IE8, is there some specific bug you're talking about?

Bear in mind that for publicly available fonts like Font Awesome, that linking to an externally hosted version might be a good choice (and works with older Moodles):

http://www.bootstrapcdn.com/#fontawesome_tab

This StackOverflow answer suggests that the font is only loaded once used, so linking when not used should be okay:

http://stackoverflow.com/questions/13249773/when-do-web-fonts-load-and-can-you-pre-load-them

edit: or maybe IE will, boo hiss!