I had largely dismissed the character of Brainiac until I saw the way that he was handled the Superman animated series. I loved that idea for the character, but I wasn't entirely sold on his look.
I didn't want the skeleton-robot version, and certainly not the silver age pink-collared-shirt-with-black-speedo version. In my mind, Brainiac should look a little organic, a little robotic, somewhat stately and composed, and very alien.
I looked for a while for an appropriate base. I realized I anted an armored figure (that's the way I wanted to interpret the animated series Brainiac's purple and metal suit), but I needed armor that didn't necessarily conform to traditional human sensibilities. Jor El was ideal, especially since he had those flexible tubes from his back to his arms. I popped off the Russel Crowe head, and used a fodder peg to put on a Marvel Legends Galactus Wave Professor X head. I wanted to use hat head specifically because it didn't have a lot of detail (wrinkles and such), which makes sense for a synthetic being, and the face was nearly expressionless (except, perhaps, for a barely perceptible smirk.

I dremeled the "S" shape out of the chest escutcheon, but left the other "alien" details. Then I sculpted the three trademark dots on the escutcheon and forehead, and sculpted some details on the neck and up the back of his head to make a nod to what his neck looked like in the animated series. Purple paint for the body suit, silver metallic shades for the armor, a subtly metallic green for the face, and small pink "lights" wherever it felt appropriate on the sculpt to make a nod to the "New Krypton" outfit.
I have to confess that the base is what "makes" this custom more than anything I did to it.