
I'm planning to do it on 18ct aida or an even smaller count, because I predict the size will be enormous due to the detail. I don't really have a constraint as to the size or number of colors. As small/simple as possible while retaining detail, would be my preference, erring on the side of preserving details over simplicity. For example, it's important to me that Illidan (the green, horned/winged figure on the right of the large bottom panel) be quite clearly recognizable.
For those wondering, this is the same, very talented artist who did the LOTR stained glass pieces that were very popular on here a while ago! breath-art on DeviantArt.