Décor is not something to be concerned with as they will most likely dislodge and eat any plants that are added and they will attempt to eat any plastic or cloth plants that are added as well. There are some submersible logs or tree like décor that I have seen used but that means there is more to clean. There is also no valid reason to attempt to add a substrate to the aquarium. This will generally result in the turtle swallowing a piece of gravel. If you must have a substrate I would buy the 1” river stones.
You will also need some type of floating log or turtle raft or whatever you want to call it. You can use cork bark pieces too. Whatever you use, secure the floatation device beneath the basking spot so that the turtle can completely haul itself out and dry out. Writing this the day before Fathers day reminds me of a story my dad told me about fishing with his Grandfather. “We were in a boat on the Green river in Kentucky and Grandpa noticed that the mud turtles were all diving into the water. He turned to me and said ‘boy we got to go its fixing rain’ I asked him how he knew that, and he pointed out the turtles behavior.
I asked why they were going into the water and he said ‘Cause they don’t want to get wet’ we rowed home and sure enough one heck of a storm came down the river that day with an hour of us leaving.” Whether those turtles actually didn’t want to get wet or not I have learned that my dad was right when he said “If you watch the animals they will tell you what’s going on in the world.” I miss you dad. Next