What about a quasi-Swadesh list, displaying corresponding terms in several languages? The problem is that terms like "linguistics" will be loanwords in most languages, so I'm not sure how to tie it into the ad.
Maybe use the words for "language", "stack", and "exchange". English in bold, on the left.
English Dutch Spanish Lithuanian Russian Greek Albanian Hindustani
**language** taal idioma kalbà jazýk ghlóssa gjuha bhāṣā
**stack** stapel pila ? kúcha sorós grumbull? dhu'ām̐rā
**exchange** beurs bolsa birža bírzha khrimatistírjo bursa bājār
Linguistics Stack Exchange
(The "stack" translations should really be for the computing term, but those will just be English loanwords so it doesn't really work. I'm using Indo-European languages for now.)