I ordered some cheap plastic palm trees off Aliexpress, and they finally arrived. They're a bit rough, but at something like a dozen for £2 I am happy with them. I drybrushed the trunks and fronds right on to the plastic and they look not too bad. I am mounting on them bases for stability; here's the completed first one.
As you can see, I've added some beachfront real estate to my islands/hills by buying some sandy-coloured felt from Hobbycraft. It's 55p a sheet, and I just cut it to make irregular shapes that I can use as sand bars, beaches and so on for the islands. It adds some verticality to the terrain, which is nice, and I'm going to make more.
The water is just turquoise crushed velvet. I got enough to cover my table on eBay for about £4. It'll form a shallow-water base, while the islands and beaches are connected by a network of docks, stepping stones, reefs, bridges, and so on. The fallen tree in this shot comes from a kids' playset I got at a car boot sale and actually holds up a figure pretty well.
The coffee-stirrer walkways need a little weathering, but they didn't take long and I can make more of them easily, so I'm happy with them.
And of course, I've been collecting relevant bits since forever, so lots of things get reused. I do like these Lord of the Rings ladders, which actually hold up a plastic miniature pretty well.
So yeah: warband finished, terrain coming along nicely. I think I'm about ready to start playing!