The corps flags for the Army of the Cumberland were different for Stone's River.
According to General Order 41 issued on Dec. 19th, 1862, the Center Wing of the Fourteenth Corps was to be a "plain light blue flag." 6 feet on the staff by 4 feet on the fly.
You have to remember, at the time of Stone's River, the entire army was designated the Fourteenth Corps. After the battle, the Right Wing became the Twentieth Corp, the Center Wing the Fourteenth Corps, and the Left Wing the Twenty-First Corps. So if you are looking for what would become George Thomas' Fourteenth Corps, that would be the Center Wing at Stone's River.
However. The General Order was only issued on Dec. 19th. Just speculation on my part, but I'm not sure that is enough time to have created and issued these designating flags in time for the battle on the 31st. Unless they were sourced locally somehow. But I have no records of that.
Also, the acorn was only adopted as the symbol for the Fourteenth Corps with General Orders No. 62, on April 26, 1864. So the flag on your initial link was issued after that date. It may even be very late 1865 or post war. The Army of the Cumberland had changed its HQ flags again for the Atlanta Campaign, and the one at the link is not it.
prepares to do some regimental-level ACW gaming.
