It has the heart of a really nice tank. I think the mix of sand and gravel is nice (but then I often do that myself) one when you get patches of gravel showing through, it looks really natural.
Anyway, a couple of thoughts: I'd make the "dunes" a bit less even, right now they look like a sine wave. Too artificial. I'd either have just one peak at one end, and a trough at the other, or create two peaks but one much smaller than the other. Given your tank is rather short, I think just having a single peak will work better.
Try and find a way to combine the bogwood with the sand, so that it doesn't look like a lump of drift wood but rather a tree root exposed by the shifting sands. Perhaps place the wood on the glass at the bottom, and then mound the gravel and substrate around it. In fact, this is a good ploy generally because it avoids the problem of food or waste getting stuck under the wood where catfish and snails can't find it.
I'd also try a mixture of short and tall hairgrass. The dwarf stuff is nice, but the tall stuff (which I've discovered you can buy VERY cheaply as a marginal/shallow water plants for ponds at garden centres) gets to about 30 cm tall. A mixture of the two dotted about the tank would turn it into something that would look very much like a salt marsh but with the tide come in. Then add a few fish like livebearers or halfbeaks or glassfish or dwarf cichlids and you would complete the illusion. It would look marine-y, but actually only freshwater! Add a few freshwater shrimps and snails, and whammo, your very own saltmarsh.
You might find the crypt will stick out like a sore thumb though. One thing I've discovered (after spending too much money buying plants) is that recreating biotope aquaria works best with one or two species of plants rather than lots. And the species need to have the same general shape, tall and willowy, or short and bushy, or whatever. What works in an Amano "nature aquarium" doesn't work in an authentic natural aquarium. Amano-style is about suggesting a landscape rather than recreating a habitat.
Anyway, looks great.
Cheers,
Neale
Get that dwarf hairgrass as a carpet, tbh thats about it, the rest is awesome