The outposts read "Outpost 20", "Outpost 07", and "Outpost 87". Of course outpost 20 symbolizes Orion opening in 2020, outpost 07 symbolizes Firehawk's relocation to Kings Island in 2007, and outpost 87 symbolizes the opening of Vortex.
I believe there are also several easter eggs where the FoF pictures used to be. I think there was a seat from one of the Firehawk trains, and some cans that say "Firehawk Hydro Fuel", and maybe some other things.
I know the barrels are kind of obvious in what they are referencing, Like Radium xl-200, and Sedimentary 325, But one of them says "Metamorphic VTBC" which vtbc means Volcano The Blast Coaster.