How do you decorate the bottom of a pond? Fake stone or gravelpicture

My pond is doing good but the black colored bottom of the preform I have
is to plain looking. Is there anything I can get to lay on the bottom?
Like maybe a fake picture of gravel or pond stone? Maybe something that
can handle being in water all year. I had real gravel and no way will I
do that again. I dont want real stone either. Just some easy to clean
item. I know most say its good bacteria ect, but Im not going that
route. Any one have any ideas here? I have some green plants but my
turtle loves them and eats them, I wont give up my turtle. LOL.. Thank
you.