Hey welcome to world of aquascapeing, think about the live stock e.g some will need caves and think about were you might want to place corals in the future, my advice would be firstly have some clearance as you will definitely need to clean the glass, open it up dont clump it all together or it just looks like a lump of rock which you cant see behind, fish and inverts will hide in spots and you wont be able to see them which is part of this hobby watching your livestock, experiment with levels have some high have some low some times it fun to see an invert just hanging on a rock high up in the corner some where and have some empty spots between the rocks as it's fun to see the fish swim in out of them, there is a plethora of images of other reefs take some inspiration from them, aquascapeing is not just about how YOU want it to look but what your livestock will enjoy and feel comfortable in. This is just my advice you can take it or do whatever suits you just remember your reef will mature and as it does so will you and what you think looks nice know might not be practical for fish, inverts and corals in the future. Good luck i really hope it goes well most important is have fun with it dont let it frustrate you and keep experimenting. ✌