Vary interesting topic! I think the best way to do the gnomes is part costume part CGI especially sense SC will most likely have a lower budget and I defiantly would like them to be varied in appearance like in the book although that might difficult to do.

Hmmm, not entirely sure how I would like to see them portrayed - I guess it would be nice to somehow convey the fact that they are a different species to the dwarfs. Whether that's through scale replacements, extensive use of prosthetics, or full CGI characters i'm not sure, just as long as its substantially different to how they did Trumpkin and the rest of the dwarfs in the previous movies.

In terms of voices I think I would have to favour a Northern UK accent of some sort - something with a really earthy sort of quality to it.

I'd like to see the gnomes done with well done costumes - maybe with some CGI enhancements. Maybe they could do something similar to Where the Wild Things Are: have actors in costumes with CGI faces. I thought that worked really well. It gave the Wild Things a physical believability, while still giving them good facial expressions.

(Here it comes... another LotRs comparison )
There was a shot in Fellowship of the Ring that comes to mind as an idea for the gnomes in Silver Chair. It's when the Fellowship is racing through Moria and the goblins are closing in on them, they're surrounded, and then the Balrog shows up. In that one close-up shot, the goblins are a mix real people with CG enhancements. I was always impressed with that scene because it was hard for me to distinguish was was real and what wasn't.

So... that's what I would suggest for the gnomes. Have some short people, some normal sized people, and some giant people playing the roles of the gnomes, and then mix in some crazy-sized CGI gnomes as filler.

I'm really looking forward to seeing what the gnomes look like in the story; the design team can really run wild with creativity here. I do hope that they don't try to make them look particularly scary, though: I think we're supposed to feel more inclined to pity them than be afraid of them.

I think I like the idea of costumes and prosthetics with some CGI thrown in. It should make them look quite a bit more "organic" while also making it easy to believe that this is a species that is not human at all.

One thing about the gnomes that I insist upon is variety. It is clear from Lewis' description and Pauline Baynes' illustration that the gnomes are meant to come in all different shapes, sizes, and features. I would compare them to dogs: all the same species, but they can look wildly different from one another. I've always sort of imagined them as being uniform in colour...kind of like someone took a big piece of grey clay and moulded it into a whole myriad of creatures.

And definitely not scary. Sad and weird, but not scary. It's not like they're menacing or anything, they're just odd.