im sorry this has not to do w/ the rock back grounds although this may help
MagNaturals Rock Ledge
but i was wondering rob, is your picture a toilet seat w/ thumb tacks on it?
i went through my archives but and google, fustrateing i cannot find what i am looking for, someone on this site made a post w/ a link i had gone to some months ago.
there are some foam rocks that this company makes, very realistic and these rocks come in many many shapes and sizes full of pot holes just like real rock, made of a foam w/ magnets in them allowing them to stick to walls, coraline algea grows on them just like near by corals, they help make any tank look great for fresh water too. im sorry, maybe a new thread about foam rocks will bring up the page.