I see what your doing and your doing fine, but, what you need is more rock actually. Draw a rough idea on paper how you want it, aka, cliffs, caves etc. Start building from left to right to your drawing, not cheating out, and, when you run out of rock, guess what, time for more!
I think you're off to a great start, but I agree that you need more rock. Be careful not to let the rock get too close to the glass on the sides. You'll want to leave enough room to squeeze a mag float passed the rock when you clean the glass. It's usually a good idea to place the rock before the sand, but it looks like that ship has already sailed. You seem to have a lot of sand in there. Deep sand beds had their day in this hobby, but they can create some real problems down the road. I would suggest that if you want the dubious advantages of a deep sand bed, you do it remotely. Putting no more than 2" of sand in the display tank for the sake of appearance is probably the best idea for someone new to the hobby.
i agree youre off to a great start, but will need more rock. and aquascaping is all a personal thing, what I think looks good you may think looks like utter crap. I prefer to get my rock up high and leave ledges and diff levels to place new corals. just make sure, like someone said you leave room for a magfloat scraper, and when in doubt give them the nudge test, gently nudge the rocks to make sure they are not going to fall over on you at the wrong time.
If it is a reef tank, keep one thing in mind. You need surface area to place corals on. The scape of the rocks will slowly diminish once its fullof coral. Dont make the aqua scape so that there is shadows on the rocks where the light wont hit.
What livestock are you planning? Most people believe it is best to place the rock directly on the bottom of the tank. If you place the rock on the sand, animals can dig underneath and cause rock slides. When I did my tank, I chose large rocks to lessen the chance of rock movement. I have rocks across the entire back of my tank. Sometimes I wish I just had some rock in the center of my tank so the fish had more swimming room; however, the fish are probably happier in the present configuration because they can hide when they feel threatened. Also if you plan on keeping corals arrange your landscape so there are spaces to place frags. Many corals take up more room than you think when they grow. Good Luck. For me the planning and construction phase are just as much fun and having the tank up and running.