I've politely urged him on Twitter to describe how these work, but he tells me these two are too precious for him to reveal the secret.
If you want a demo of what it can do and the original Nvidia paper/video isn't impressive enough, check out the anime faces I've been generating with just a few days of training on my 2 GPUs: https://twitter.com/gwern/status/1093701790971953152
For H.R. Giger pictures, I suspect the problem is that you simply don't have enough. StyleGAN is powerful enough to memorize datasets of under a few thousand images. What I would suggest is that you might be able to take the Nvidia 1024px face model or cat model and retrain the model with your artwork; that saves you sample size, and to the extent that faces or cats remain in your final model, well, perhaps that will just make it creepier or hilarious, in the vein of 'dogslugs'.
(This is what I have been doing to make individual-character anime-face StyleGAN models: few characters have so many faces as to be able to train from scratch, so I've trained a StyleGAN on the entire face dataset, and then I simply retrain it for an hour or two on just that individual character's faces to finetune it.)
Alternately, you could try to borrow strength from an illustration dataset somewhat similar, maybe a Western art dataset like WikiArt? (I forget if WikiArt is the dataset OP mentions Mario training his GANs on.) Train a StyleGAN on that and then do transfer to Giger as above.
Finally, you could get more invasive and try to weaken StyleGAN enough to make memorization more difficult when training from scratch. Shrink the 8x512 FC layer stack and remove filters from the convolutions, for example. It will be a lot weaker but it'll generalize better within the samples it's still able to generate. Train faster/smaller too.
I really hope he sells it at a high price.
The value of art is not something you can quantify this way.
For something like this, anyway. The point isn't that anyone could build it in a weekend, but that someone with the contacts and the required business/commercial network knew how to build it and sell it.
It will probably be bought as investment with a view to profit on resale.
What he does is not just firing up a GAN and sampling some pictures.
He's an explorer navigating uncertain realms. https://mobile.twitter.com/quasimondo/status/106311763402625...