Overall, I think they're quite good. Lot's of high quality art, good design. I especially like the overhead views from the OP.
But I prefer to judge some things by the lowest resolution drawings rather than the highest resolution. What will these dragons look like as computer icon or a thumbnail? Maybe it's just my 8-bit gaming history showing, but I think how designers communicate under more minimalist circumstances is pretty important. Is there enough difference that a color-limited person like myself can tell the chromatic dragons apart when they're shrunk down below mega-pixel scale?
Does anyone have any examples of how this might appear outside of the high quality previews shown here? I'm looking for things like the tiny picture in the corner of a book, not the cover.