Thanks for the input. I actually was thinking the background I have may clash with the rock, too. Don't know if I want to just remove it, or replace it with dark blue or black.
As far as the rocks there now, I have them almost touching the back of the tank, now. I just intentionally left an area behind so I can clean when I need to and for the fish to have room to move behind there. I may add some more height to it, but I sorta set it up for the long haul, so every rock is balanced and stable and won't fall; plus, it gives them plenty of caves. I may change the structured look eventually, though.