Okay, so Kirby drew the Kree Supreme Intelligence once and never again. Here’s what it looked like:
When other artists picked up what Kirby created they interpreted this as a giant floating disembodied alien head:
But looking at Kirby’s original drawing, it looks to me that within all that crackling energy, there’s the suggestion of a slug-like, worm-like body. Something akin to God Emperor of Dune. Here’s what I imagine it would look like:
The added tendrils are optional. One last bit of speculation: just like Captain Marvel was a Kree version of Fawcett’s Captain Marvel, I wonder if The Supreme Intelligence was a Kirby-ized version of the Shazam villain, Mr. Mind. It would seem natural for Kirby to introduce an imposing character like this, who the heroes later discover is a tiny tyrant, similar to what Kirby did later on with Overlord in Mister Miracle #2.
Kree Supreme Intelligence, Captain Marvel and all that jazz is TM and copyright Marvel Comics.