I agree with VJM on darker substrates. They hide the mulm that bugs most people on lighter substrates because of it's darker nature. It also make the tank's inhabitants' colours pop. And seeing that you already have light rocks, you could get some dark substrate and sprinkle some of the light rocks over it (or get some dark gavel and sprinkle a bit of it over your light gravel). I've seen a few do that and it looks very esthetically pleasing.
As for plants, the usual suspects (java fern, java moss) will work well. Personally, I'd get some suBwassertang and scatter it over the bottom of the tank (cause I love it... it's my favourite plant and it's super easy to care for), wrap some java moss around the top part of the driftwood and tie a few java ferns to that (also on the top) to add some different levels to the tank. I'd throw some stems into the back as a backdrop (I like sunset hygros, but there are many other options (plus those are a noxious weed in the US, so sometimes they can be difficult to get a hold of) and add some type of floater; dwarf water lettuce looks really nice and has very pretty roots that hang down into your tank. As far as I know these are all low maintenance plants, as far as growth is concerned. Once your system begins to flourish and grow you will need to keep on top of trims, though :D