Brainiac's head diodes were simplified into three circles in a triangle pattern for Superman: The Animated Series ("Last Son of Krypton, Part 1", 1996). This was later loosely adapted as a special marking that indicated Brainiac 5 had upgraded to Brainiac 5.1(Legion of Super-Heroes #104, May 1998), and more strictly adapted as Brainiac 5's logo in Legion of Super-Heroes #37 (February 2008). Later that year, it was used by Brainiac himself in Action Comics #866 (August 2008).
For a while in the New 52, it looked like the Brainiac symbol was done for, because Brainiac showed up like this:
But in the teaser for DC's new event "Convergence", it shows up in full force, right on his chest. Now, whether this is the same Brainiac or an alternate one remains to be seen; nevertheless, there is a Brainiac that still uses the symbol: