I had to laugh reading the Sixth Circuit's ruling in the Mercer County case, which looked at a courthouse display of the Ten Commandments and other "heritage" documents, identical in fact to what was before the Supreme Court in the McCreary case, that the display in Mercer County did not violate the Establishment Clause as construed in the McCreary case.
The ACLU lawyers had to scratch their heads over that one.
So, the difference, according to the Sixth Circuit, is not just what the display says, but the history of how it got there. The County in McCreary lost in court before changing its display, while the litigation record of Mercer County was pure. Since Sullivan County, Tennessee, is in the Sixth Circuit, I have to conclude that there is at least a chance that the Sullivan County display might pass muster, at least with one panel of the Court of Appeals, notwithstanding the pessimism of the County attorney.