Hmm, haven’t come across the language icon before: <http://www.languageicon.org/>. Unfortunately, it looks rather shabbily done and very abandoned. Serving a JPEG for the large image instead of a PNG (to get an alpha channel while still being easily copyable) or SVG (for best results except for most copy-and-paste purposes), speaking of 2013 in the present tense, no HTTPS, claiming “copyright and hassle free” but it’s actually using an extremely problematic barely-specified license (claiming “a CC license” with no link, and a whole bunch of terms so that it’s a poorly-modified CC-BY-SA-NC), claiming you can download “rar or zip” and it includes SVG and more but it’s actually ZIP only with an eclectic mixture of bizarre formats (not including SVG), colours (some obviously wrong) and sizes, the icon itself is not aligned to any sort of sane grid and has been hand-placed and angled… all up it’s an unhappy mess. That’s not the way to go about trying to make a universal language icon that you want adopted. Pity, because the idea is decent (though the original article is quite correct that labels are far better than icons anyway).
Please don't. Flags are not languages. (http://www.flagsarenotlanguages.com/) There are many languages which cannot be clearly distinguished with a flag icon -- for example, there are dozens of languages which could be represented by an Indian flag (Hindi, Bengali, Telugu, Urdu...), and some languages which don't have any clear flag, or whose flag could be politically complicated to display (like Catalan, Romani, or Tibetan).
Use the localized name of a language to indicate the language (e.g. English, Español, Svenska, 中文). It's unambiguous and takes very little effort to implement.
On the contrary, if you just use the name of the language then it's not at all clear to a user who's using the "wrong" language where the language selector is.
lmm may be suggesting the use of flags as iconography only for the button that opens a popup where you can choose a language. That would be somewhat less bad.
Iconography already exists for that. On Windows, it’s a symbol comprising an A and a 文. On Apple systems, it’s a globe icon. I think the globe icon is seen more often on other platforms and on websites. Having the localised language name next to the icon helps, too.
