The gravel alone looks nice already

Thinking of a community freshwater tank? You know, the kinds of fish should determine the way your tank will look. Or, you should match the fish to the particular setup you want. Do you have any specific fish or any specific setups in mind?
There are lots of center pieces you could have, depending on - like I said - the setup type. I personally love planted tanks with driftwood because they provide most natural looks. And I like anything that looks natural. If you'll have the usual community fish like Angelfish, Gouramis, various Tetras, etc ... then plants would look very nice in such a tank. If your lighting is standard and your gravel is inert (i.e. regular non-nutrient-rich gravel), then get some low light plants. I am afraid Amazon Swords won't do well under standard lighting, but if you want, you can give it a try of course. Great low light plants that don't even require any substrates are: Java Ferns, Anubias, and Java Moss.