Adding rocks created a little more dimension to my tank, but it still wasn't enough. Around the same time I set up the plant tank (or perhaps it would be better to call it a plant nursery, since that is how I originally envisioned it) and purchased a few more plants. Perhaps it was serendipity, but I got some new Cabomba and Water wisteria (Hygrophilia difformis), together with some new Ludwigia. Without high-grade lighting and CO2 injection, I am not going to be able to establish the sort of super-dense garden tanks that are so popular these days. I shouldn't be trying to mimic those setups - I need to work on producing the best aquascape I can, given my constraints. But I can still learn from them without resorting to a crude caricature, a child's imitation.
Although it didn't start well, I have been very happy with Cabomba. Initially it became very stringy, elongating its internodes in a push for the surface of the water. But now, it has thickened up pretty well and filled out. But trimming and replanting the tops, I have the makings of a nice little Cabomba forest. The cut stems have resprouted, and a few uncut stems have also sprouted. While it doesn't seem to match well with modern ideas about aquascaping, it has a "natural" feel to me, the feel of a macrophyte-filled lake. The water wisteria were planted in an area behind the driftwood, adjacent to the smaller of the Echinodorus. The divided leaves emerge from an area dominated by shorter plants with narrow, elongate leaves. I like the effect, but it's a little asymmetrical.
I recently read an article about Dutch aquascaping. While the practice stresses garden-like layout and terraced arrangement isn't something I plan to implement, I was struck by the idea of using "pathways" to create an illusion of depth. I really think that's something I could make use of.