I'm over 1000 credits into Dalle so far (I know, I know..) and you're on the money. You can go a lot further than impressionism, though. Specifying the names of famous illustrators, photographers or artists. Specifying the media used. Lens types. Colorways. Film types. Lighting. The right combinations can yield some incredibly realistic looking things, even faces, and then for the rest of it, there's Photoshop, Gigapixel, and other tools to patch things up. (I've had more luck creating 'elements' with Dalle and then montaging them the old fashioned way.)
The images used in the blog linked by OP are okay but stylistically all over the place. OP acknowledges how difficult good prompts are to write. Beyond that, though, you still need to think like an art director and establish a way to set a common style to avoid jarring the readers, and Dalle alone can't do that.
> Specifying the names of famous illustrators, photographers or artists. Specifying the media used. Lens types. Colorways. Film types. Lighting.
Are training sets prepared with systematic variations in individual axes, as an alternative/addition to tagging each of millions of training images on these axes?
The images used in the blog linked by OP are okay but stylistically all over the place. OP acknowledges how difficult good prompts are to write. Beyond that, though, you still need to think like an art director and establish a way to set a common style to avoid jarring the readers, and Dalle alone can't do that.