I wouldnt worry about the "stump" lol, I like the hole and if you do too who cares. Definitely needs more headstones though, would be a pretty lonely graveyard with 3 stiffs
I love the idea here, very fun! What plants are you gonna use? Hopefully some dwarf hairgrass, would look awesome like an old overgrown graveyard. You could paint little pictures of white skirt tetras on the stones lol. maybe some green shrimp in there too?