It actually symbolizes grass or a field for grazing. See, even 'satanic magic' has a certain amount of xerox copied imagery.
Part of that imagery is for everything to be dead or dying, but more likely because they read it in a book or saw someone else do it. Exhaltation of death on the LHP died in some Aghori graveyard.
The only way to do an altar correctly is to make it a decorative piece a la dios de los muertos. Just give it the vibrance of a Diego Garcia painting. You know, all that candied mexi-shit.