You'll get something that feels right. Is this your second planted tank? I see you have a 5.5 gallon.
That's a lot of substrate you have in there. I would either remove some, or make a STRONG slope toward the back. Try to keep the font of the substrate just barely higher then the black trim on the bottom of your tank, and maybe keep the rear just lower than your filter intake. That alone will make the tank at least appear much larger than it does now.
If you keep the rocks whole, maybe try laying them horizontally, with about 1/3 to half of each rock buried beneath the substrate. Sort of stagger them in the mid section.
If you break them you have a little more to work with. You could stack the smaller pieces to create sort of a terrace wall, and pile substrate behind for an elevated planted area. You could also make rubble piles, and tuck in different types of anubias or java fern.
Hard to describe, but if you keep experimenting, something will come to you. Take a break if you need to and look at other people's tanks or browse the aquascaping section. I bet you'll get something cool going.