I'd say add a dozen or two cories, some more driftwood, and another Aqueon. 55/75 would be ok, 110 would be better. you could do some more danios or equivalent.
a 2 lamp T5HO fixture will let you grow a sword plant or two, some anubius, and some Dwarf sagittaria.
X2
To be even more specific...
If it were my tank I'd plan on adding 6-12 cories most likely Corydoras sterbai as well as 3-6 more danios, just to add to the movement. As far as filtration, I'd look into a decently priced smaller canister filter, something like a sun-sun 303B or a Rena XP3 (both around $100) either should handle your tank and would do even better along side your current hob. I'll agree with Gill on the 2 lamp T5HO as far as lighting (this is a solid, reliable choice) but don't be afraid to look into led lighting as well, I'm a fan of Marineland and as long as you stick to low light/low tech plants ie: swords and anubias, etc. then you should be covered in the lighting department only using something like their double bright fixture.Your fish will enjoy a few more plants and by adding only a few leafy greens to your tank you'll get the added benefits of extra deco and filtration.
Concerning deco, I'm a huge fan of how simple and attractive the layout is in you tank, I know that you stated that you eventually plan on adding some type of 3D background but in the mean time I think you'd really enjoy a black background, as it would make your fish really pop and give your tank a more completed look. Not to mention, adding a background to the exterior of the tank is about the simplest thing you can do as far as deco is concerned; paint, poster board, fabric, tint, vinyl, etc. just pick your poison.
good luck finishing up the tank and make sure to keep us updated!