I might suggest repainting/cleaning those overflows though.
Lighting looks a little too blue for my taste, but see how it looks once the greenery is in there.
I had a feeling it was a previous saltwater tank (also why I was thinking the lights might be higher spectrum blue), so I suspected those were mineral deposits, or just paint chips.
You can use something acidic, like vinegar or a stronger acid (bar keepers friend works great and is safer than stronger acids) to dissolve the calcium deposits quicker.
A clear (back wall of room) or lighter color background might give the tank a more natural feel, but those black overflows may throw that off. Get it looking how you want it first though and then you can decide on the background after it's all said and done.
Plans for fauna?
Going high tech? Not sure how much co2 the overflows would off gas.
Hahahaha, Got to persuade some how
I will let the light experts comment on the plant growing potential of those lights. But with my minimal knowledge on those lighting, those throw out plenty of blue light (most used by plants, but they do like some green and red spectrum), so you should be able to grow most things, but the plant colors may not be at their highest potential, and the blue hue projected from the lights themselves may skew viewers perception of the colors.
Got the dimensions of the tank? (height mainly)
Acidic liquids would have made the mineral clean up much easier haha, next time.
As for lava rocks, smaller pieces would provide more surface area per volume. Lava rocks has tons of external craters, but those pores don't tunnel through the internal structure, so water contact is only limited to the external areas of the rock. You could crush up the large chunks of lava rock, but easier to just buy them already small sized. The large lava rocks are just wasting space (unusable center core, no water passes through)
Nylon pot scrubbers, like the packs you can find at the dollar store, are another good cheap option. They provide more surface area. Clog less and easier to clean I believe?
But if you aren't stocking much fish/bioload, and you are already going to have a ton of plants, there's not too much need for a lot of biological filter media. Still surface area wise, I would go with pot scrubbers over crushed up lava rocks.
Got any pics of your old saltwater tanks? Wouldn't mind seeing some.