Forget about planting since these turts are major plant-eaters. The only FRT planted tank I've seen had a false back glass panel installed with live plants situated behind the glass pane and away from the FRT. Driftwood and caves are your best bet. Large rock pieces are also a good idea if the tank has strong current. The large stones provide a current break area where the turt can rest without adjusting for the water current.
And, as was said above, replace your gravel with coral sand/aragonite sand. It'll provide the alkaline conditions these turts prefer and prevent lesions (such as the one under his neck) caused by coarse gravel.