I keep coming back to the basics that I learned back in the day, and they hold up over time. In this case, don't be afraid of big, bold highlights.
With this army, I really wanted a realistic, subtle look. I wanted the cloth to clearly be black, but highlight it with a tint of blue to match Gandalf. Plus all of that grey and silver would be really boring.
Sadly, I went too subtle, and you couldn't see the highlights outside of highly exposed web photos. So I went back and put a bold highlight that finally accomplished what I wanted.
On the right is a model that I haven't touched since the Gathering. This was one of the ones with the most obvious, bright highlights. Yeah, I'm not sure that either of those terms apply there. The middle one is a model that I've black lined, which did help a little, but didn't make up for the dark highlights. The left is one I just finished highlighting the cloth with Shadow Grey. MUCH better. Don't let the chunkiness of the highlights fool you - when they aren't in the bright light and up close, those highlights really make the model work.
This back picture is a much clearer one of how well the highlights work. Notice the blacklining I put in place around the hair, armor plates, and between the armor and cloth. Combined with the bright highlights, that really works.
And here are all of the warriors of this pose highlighted with the new cloth highlights and blacklining. I currently have the lights off in my work area and am looking at the models with ambient light, and the difference is striking. The unhighlighted models are flat and dark, while the highlighted models, while still kind of dark, are much more dynamic.
Oh, and I figured out why my new camera wasn't taking bright pictures. Since I don't have a manual shutter speed setting, it was taking an overall view of how much light was coming in. With the background being white, that told the camera it needed to have a much faster shutter speed! Now I feel dumb.