One of the first things I wanted to do with Oli's blog was start making minor alterations to the default Kubrick theme (which I really like, incidentally) in my favourite vector graphics editor, Inkscape. However, after searching the web for the source, I eventually found that the original source was a Photoshop file - one that the GIMP couldn't open.
Frankly, I don't think this is a very good show for an application which purports to be open-source. Anyway, as a result I pulled Wordpress's assets into Inkscape and reconstructed the graphics, as closely as I could, tracing the originals.
The result is an SVG file and a shell script to extract the assets. The assets should all be replaced together because the match isn't quite pixel perfect, but if you do replace them you shouldn't notice the difference.