Have you ever considered using a darker substrate?
Doesn't have to actually be dark but something with a more neutral, earthy color.
I think the shellies would look much better, not quite so washed out.
Aim for a tan or brown! The brevis will look good over darker substrate but gold occies tend to wash out over light substrate and really muddy out over really dark substrate. Good lines are also important in really nice gold gold occies. I think yours have great potential!