Forget private property, I assume you know you are in the wrong there. Municipal cemetaries are generally off limits after dark whether posted or not. Most private church owned ones are too.
As for IDNR properties including State Nature Preserves, Parks, reservoirs, boat launches, et. al. There are state regulations prohibiing camping except for designated camping areas. A good way to tell is if you didn't see a sign noting camping sites or someone didn't collect fees from you you were illegally camping and can expect a fine if caught.