He doesn't have to be CGI though. I think he could be done with practical effects.
I like the idea of taking inspiration from the Geoff John's Brainiac, but also they should definitely use S:TAS for inspiration. I think because Ultron is being introduced over at Marvel, it'll be less likely that we see Brainiac portrayed as a living computer basically. I think it's more likely he'll be a soulless, cold, alien, scientist, collector, and I'm cool with that, because it opens up a lot more design possibilities if his skin is organic. Or maybe he started as a living creature but now he's something else? Anyways, I think Brainiac should be a lot scarier than he is usually, and today superhero movies are allowed to get away with having scary villains. I think they should take some cues from H R Giger's work.
Replace the tubes from this dude's mouth and eye, and have them in the classic triangle formation on Brainiac's head