Looking really good, especially so for a first tank! I love the substrate and the plants you have.
If you think it needs more, go to your LFS and check out what hardscape is available. There might be a piece of driftwood or a big rock that you just have to have. If you have something too specific in mind, like trailing branches, you might get frustrated and not be able to find something that looks exactly how you want it. See what's available, see what grabs your attention, then (after preparing it) stick it in there, shift things around, and decide what you like!
I find it helpful to arrange the rocks and driftwood, step back and take a photo of the whole tank, go back and re-arrange, take another photo, etc etc. I keep doing that until I run out of ideas, then have a gallery of photos to look through, and decide what arrangement I like. I look at images of other planted tanks and videos on aquascaping, and draw ideas and inspiration from there. Take your time with it and have fun, and now is the best time to do it, before your plants fill out too much, and your options are wide open.
Have a look at what the rule of thirds is in aquascaping too, it can help a tank look more natural, but it's also a guideline rather a rule, and you can also ignore it completely and do what you like with your own tank.
Have fun and share photos please!