Actually, don’t let base64 scare you too much with this. It’s generally scripts that contain base64 that are more of an issue… The theme uses the embedded fonts so there is less http queries which helps for performance reasons. Fonts are huge when you link to them. The base 64 for embedded fonts is actually ok. However, if you are worried about data URI fonts, you can go to Google, download the fonts used in whichever theme you are using (I’m assuming Circumference), then use Font-squirrel to generate the @font-face which you can then put into the style.css file in replacement, then add the fonts to the fonts folder. For the icons, the download package already contains the font files for icomoon (the social icons and more).
As a side note, I use base64 fonts in my Styled Themes website.