Ok, I had to copy/paste as I am not at home. Here's a impromtu shot of an EL and N. leleupi contrasting against crushed coral which you were thinking about:

I have black sand in my Truvu 75g long which also has a black back. I don't keep my EL's in there but I could try to put one in and take a shot of him. Trust me, it doesn't work as the definition of their own black marking gets blurred/lost with the black sand and backing.
Once home, I can take some shots of my EL's against the CC.
I have black sand in my Truvu 75g long which also has a black back. I don't keep my EL's in there but I could try to put one in and take a shot of him. Trust me, it doesn't work as the definition of their own black marking gets blurred/lost with the black sand and backing.
Once home, I can take some shots of my EL's against the CC.