It's like art... it has to appeal to you, not everybody. Some like a clean look, others a natural scape. By your placement of things in the tank I'd venture you are neat and organized person. It all just seems to placed... and not cohesive (you have too many diff looking rocks, like 4 different kinds). I'd stick with many of the same. And yes, the scale is off on those swords I think but you could leave them until you get smaller plants in. Start with different rocks and experiment with making shapes in the tank with your rock placement. Google "aqua scapes in small tanks" and see what you like. Notice how some hardscape placements create a triangular form or repeating diagonal lines, or bowl shapes. Also, don't be afraid to try a slant to the substrate in the future. Many add depth by using a hill concept with their substrate. It's not a rule but many give the appearance of more space by using shorter plants in the front and the taller in the back as mentioned. You can even consider the bird's eye view from above and create curves to draw the eye in or to add interest. You can really make a big impact with rock placement so as a first step I'd set some rocks out on a towel and try arranging them until you get something you like. Your tank looks clean and the fish look happy, just keep going and keep looking online at what appeals to you, then try to replicate it. Start with the rock placement... maybe just add more small rocks and create one hill off center to begin.