I have made a little more progress on my thread painting:
I promised some close-ups, so here they are!
This is one of the mountains. I don't think my thread color choice was great in this, but at least it shows up well in the picture! The top is done with a straight stitch, moving the fabric relatively quickly. The curvy contours are done using a zigzag stitch and moving the fabric quite slowly. The piece is held at an angle while doing that:
Here is a tree line. The top is done the same way as the top of the mountain. The inside detail is also a zigzag stitch, but this time I moved the fabric faster, and it was at a 90-degree angle to give that up-and-down look. At the bottom, there are some reeds, which are done on a straight stitch again.
Here is the bottom of the tree and the water. Ignore the texture on the tree trunk--it's water-soluble stabilizer that was used to draw the tree branches. The swirl on the tree was a zigzag stitch, as was the stitching on the water, but again with the fabric held at different angles. I covered the water with some blue shimmery tulle before stitching.
Here is some more detail on the tree, and the foliage added. The foliage is also a straight stitch, but this time moving the fabric very quickly and somewhat haphazardly.
There is still more stitching to be done!