Yesterday I got an update from PokerStars, and now I can no longer get the old light classic display by deleting the insides of the ImgCache folder.
Now the contents of the ImgCache folder get regenerated each time you launch the client, and even if you delete them after the client is launched, they regenerate when you try to open a table.
They patched it quickly.
I cannot emphasize how much I hate the new Aurora engine, and especially their decision do completely disable the classic display despite it will cost them little to nothing.