I'll let you guys take a look. First picture is the wood planks next to the tree..don't know if someone tried to get into the base with that. Second, welp, don't need an explanation.
Not griefer stuff in the first one. Looks more like hidden chairs. Griefers don't bother to put down three plates when one will do. A position (/pos) on the second one would make it easier for staff to find the sign and clear it... If you didn't clear it already.