Nearly all the Lik picture's I've seen were ridiculously PS'd. Not only things in the scene blatantly rearranged, but ludicrously colorized. Hence my old joke that he probably hired kindergartners, put them on LSD, and handed them cans of fluorescent spray paint. That's not photography.
In one of his galleries, it was nearly all big inkjet prints, and rather poorly executed ones, technically. And loud, loud, loud ... I literally got nauseated, and had to exit after a few minutes. The disrespect for natural light was absolutely appalling ... taking nature and making a street whore out of it.
The other gallery, in Lahaina, was all relatively large sample images backlit transparency mode. Somewhat better done, but equally gaudy or tacky. Tasteless tourist fare for those who want something scenic opposite their black velvet Elvis rug.
One thing his production facility in the Vegas area is highly skilled at is mounting really big print media flat. And charging significantly for that is realistic. Throw out the print and keep the frame.
Well, to exit my rant with something a little more objective : Size should be relative to what works best for the image as well as the viewer. Not every image works well small on a book page, for example; and many sensitive classic images sure as heck don't work well when they're blown up large, big for sake of big. If someone just wants a big splash of color above their sofa, that's a legit decor decision, but so is the choice of wall paint.
I've deliberately limited my own color print size capacity to 30X40 inches (plus overall framing) for logistical reasons - size of my darkroom space, largest size that can be conveniently crated and shipped by ordinary carriers, largest mounting equipment I wanted to invest in, etc. But regardless of big or small, I fill them with relevant hue and detail content generally involving large format originals. MF comes into play as well, but certainly not in the largest prints. I don't believe in any of that "normal viewing distance" nonsense. That might be fine for airport lobbies; but I like my prints to be fully rewarding right up close too.