If you don't have a personal vision just search photos on the net and find things that you like and just replicate.
Like you already mentioned, keep rocks off the wall and make sure you have good flow.
I always like to play around and try to create depth. i can draw or email you some rock formations if you like.
Try to get something you like before introducing livestock. Many people build a scape, add livestock and continuously have there hands in the tank changing things. [thats what i did when i started] The less your in the tank - The better.
Since this is a new setup and you seem new ill give you a little advice i wish i received.
Try to find some really porous rock, I would buy extra if you dont have the chance to cherry pick and start from there. Your in no RUSH. Find rock with crevices caves and strange formations. This will ultimately help you scape. Find it, then start your cycle. If i were you i would look for some really nice coraline seeded rock. Just examine it and look for pests... Aiptasia and other nuisance algae. If you buy here, check the members feedback and ask them about the rock. Try to stay away from any rock that has no crevices and really heavy. You can always chisel and break rock to make your own formation just be careful and wear goggles.
Live sand isn't necessary but in a small tank its fine. I only say this because to buy dry sand for a nano it will almost definitely be to much sand. Live sand is more expensive than dry sand and its debatable if its even "LIVE" - any sand will become live.
Get a grip on waterchanges - matching salinity / temp etc. Practicing good habits are important. Your doing a nano tank, they have much larger swings and chances for things to go wrong but they are great once you get the hang of it.
Keep your livestock and Feedings to a minimum till you get a grip on what your tank can handle. Which will take time. Choose your purchases carefully. Stuff is not easy to get out without causing destruction!
