After a couple of days of staring at this picture, jotting down notes, and test-knitting swatches, I've figured out the pattern that forms the main body of the work. (I feel sure I know how to do the border decorations, too, but probably shouldn't say that before having tried.)
So, for any knitters out there, here it is, and although the result appears quite complex, the pattern isn't.
Difficulty level: intermediate
The pattern requires multiples of 8 stitches plus one (shaded at left) added for symmetry. Three repeats are shown here. Make that 3 horizontal times 2 vertical, for a total of 6 repeats.
Not noted in the chart is that the right side of the work is all in reverse stocking stitch. (It looks terrible in stocking stitch!) Working reverse stocking stitch means you must adapt your decreases. Thus, for this pattern:
/ is a right-slanting decrease, as viewed from the front. That’s P2Tog on the right side, and SSK2Tog on the wrong side.
\ is a left-slanting decrease, as viewed from the front. SSP2Tog on the right side of the work and K2Tog on the wrong.
O is an increase made by YO.
The up arrow is a straight double-decrease. On the right side, slip 2 individually, knit-wise, return the now reversed stitches to the left needle, and P3Tog. On the wrong side, do the same but K3Tog.
Blank squares are worked plain (P on right side, K on reverse).
The darker grid lines have no meaning other than that computers do strange things. I have no idea why they came out this way!
Note also that the lace effect is worked on both sides, thus requiring a bit more attention than patterns wherein the back side is always purled.
As always, to show its full glory, a lace piece absolutely must be stretched and blocked. As this does not work with manmade fibers such as acrylic, you’ll need wool.
What I’m planning to do instead (because cashmere, merino, and mohair can be very expensive when making a whole blanket) is knit the lace with acrylic, right into a background of contrasting color, worked in a much heavier yarn.
P.S.) The pattern looks pretty good in garter stitch, too, knitting on the front of the work and purling on the back. This makes the fabric reversible and only fractionally less gorgeous.