DeviantArt user "MisterPsychopath3001" (https://www.deviantart.com/misterpsychopath3001) draws fictional trucks in profile using MS Paint. Some of these are quite fantastic, in the sense that they could not exist.
9-axle tractor: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-Brutehood-heavy-haul-trucks-719340545
32-axle tandem tanker: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-Brutehood-heavy-haul-trucks-719340545
6-axle tractor with 15-axle trailer: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-Brutehood-heavy-haul-trucks-719340545
It's like you can hear the tire scrub as you see the pics.
40-axle triple: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-Brutehood-heavy-haul-trucks-719340545
16-axle rigid crane: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-Teralift-Ultra-Crane-589775253
Tanker train, I'm not counting them: https://www.deviantart.com/misterpsychopath3001/art/Psycauto-LXT-650-TS-fuel-tanker-road-train-619997376
For this 32-axle grain train (https://www.deviantart.com/misterpsychopath3001/art/Peterbilt-351-pulling-grain-train-721227552), a user commented: "Pulling that much steel unloaded would overtax the engine. Add weight to it, and it wouldn't be able to move." However, his concerns are unfounded, as our host replies: "Wrong, it can handle it just fine."
He also has some non-multi-axle trucks that are nice.
https://www.deviantart.com/misterpsychopath3001/art/53-Pennsylvania-Railroad-trailers-770136181