Intermediate to me means having a working understanding of all the critical foundations of visual art at a basic level, and can fabricate totally fictional images that are recognizable in what the artist is attempting in mood and atmosphere (though unsuccessfully). It won’t be close to professional enough to compete for a job in film or games, and advanced professional artists will be able to write a long list of critiques for it, but it’ll impress the average beginner or non-artist. At that level, the work probably won’t make it into the Showcase Gallery here (or maybe just barely squeezes through if a particular piece was a fluke and the artist doesn’t even understand why it turned out so good).
I sort of see it like this:
CG Choice Award - The best of the best on the planet
Showcase Gallery - Ranging from good to excellent
Intermediate - Not quite good enough to impress anyone but total beginners and non-artists
Beginner - Padawans
How fast someone grows is variable. I’ve seen people stuck in the beginner or intermediate stages for years and years–some their entire lives. They get stuck because they don’t know how to learn and practice smart instead of going in circles, or they lack the discipline to force themselves to study the things they find intimidating and draining to learn. But I’ve also seen people progress in a short few years from beginner to authoritative and respectable artists, so it really depends on the individual’s personality, intelligence, dedication, discipline…etc.