I don't know if its the angle of the photo or not, but the six smaller lava rock pieces appear to be in two relatively straight rows which to my eye looks very artificial. I would break that arangement up. If you have access/budget to my lava rock I would get another larger piece to play around with, if you have room add it to the aquascape between smaller rocks. If not then move one of the smaller pieces closer to the larger stone you currently have to make a little formation with those 2 or even 3 smaller stones. Then an empty place of just wood followed by another formation of smaller stones.
Just my two cents, the most important thing is that you are happy with it so ignore anything you don't like.