You can use some of that gravel as a top layer in potted house plants if you have any. They look decorative and will prevent any of those stupid little flying gnats or whatever from breeding in the moist dirt. They are also good to use as drainage in the bottom of house plant pots too (use some bigger pebbles to cover the drain holes then add a layer of aquarium gravel then dirt).
For the turtle's tank, a lot of us use smooth river rocks that you can get at the pet store or a crafts store or at Lowes. You only need a few to make it look nice. If you use too many, it will trap the turtle's waste and turn into a septic tank.
Also for plants, Petco sells some aquarium decorations with plastic plants firmly attached to them. The decoration helps keep the plants weighted down in the water and they look pretty good too.
Tenodera: most likely you're already aware that aquatic turtles like RES and painteds live in ponds with deep muddy bottoms where they can hide from predators, cool off in the hot weather, and hibernate in the winter. The muddy bottom is a major part of their habitat. I would guess that they probably rarely see gravel like that and in such quantities. And in the wild they have so many more varieties of things to eat and keep them entertained that any gravel/pebbles they do find probably wouldn't seem as interesting.
