All blocked now, and the ends woven in. Here are a few pictures.
The finished product:
I omitted the beads, but placed groups of three little five-stitch nupplets in the stocking stitch sections of the Agave and Edge Setup charts where it called for three beads in a triangular array. I'm very pleased with the way this turned out; they looked pretty indistinct while I was working them but stand out just enough now that the shawl has been blocked. I would definitely do this again.
And here's the closest thing I could get to an overall shot while it was still pinned out. It came out so big that it's difficult to fit it all in the frame! (It measures about 95cm from the long side to the tip. I did two extra repeats of the Yucca chart because it seemed to be a little on the small side after I'd done the number the pattern calls for. In the event, I needn't have bothered. Though I do like the size that I ended up with.)
I have one bone to pick with the pattern. When you print it out in greyscale, the chart symbols for "P on RS, K on WS" looks identical to the symbol for "place bead". As a result, I worked purl stitches in knit rows on the central spines of the Yucca motifs for fourteen repeats until I referred to the charts onscreen for some reason and discovered my mistake! Luckily it looks all right anyway, but it's still a surprise I could have done without.
Regardless of this nitpick, I love this pattern so much that I'm planning to make another, smaller version. This time I'm going to do the beads, too.