Bear with me, this is the first time I did a detailed tutorial.
String a couple of yards of your preferred beading thread through a beading needle - I used Nymo conditioned with Thread Heaven. Essentially you make a collar of beads around the hanger of the ornament ball. I did it as 2 size 11 seed beads, and a size 8, and did repeats of this until I had enough to encircle the hanger. It should fit comfortably, not too tight. If you have to force the ring, you may fray and weaken the thread which can cause it to break later, or just snap it right off the bat. The number of repeats you make will differ depending on the size of the hanger of different styles of balls - don't assume that there is one standard hanger size for all Christmas ornaments.
Then secure your circle of beads with your preferred knot - but not too tightly, and don't feed the thread through too often because each of the successive layers of beads are secured to this base collar - understand?
Then you start working the rows - for the first row, bring your needle and thread to the other side of the size 8,
pick up a number of size 11 seed beads (pick whatever you are happy with, say 12), a size 8 bead, a crystal, another size 8, and another size 11.
Skip the size 11, and feed the needle back through the size 8, crystal, and size 8 beads, (the last size 11 will now hold these in place),
then pick up 12 more size 11, and guide the needle up through to the next size 8 on the collar.
This makes your first dangle from the collar.
Then feed back through the last row of size 11s, but not the entire row, just a portion of it.
Then pick up the same number of 11s to make the next dangle even with the last, pick up the size 8, the crystal, size 8, size 11. Skip the size 11 again, and feed back through the 8, crystal, 8, pick up 12 size 11 beads.
Repeat this until you encircle the collar with this pattern of intertwined dangles.
Secure this row with your preferred knot, and thread the needle through a size 11 on the collar - to make the next row so that it is just off from the first row of dangles, as opposed to sitting directly above it. Or you can feed through to the next 8 - so long as you are consistent in the pattern.
Essentially repeat what you did for the first row, but with a differing number of size 11s, and instead of the crystal as the focal, I kept it just the size 8 beads.
Do the same for the following row, decreasing the number of size 11s used. I either change to a different colour of beads here or in the last row.
For the last row, pick up a short row of size 11, the 8, and 11. Skip the 11, feed back through the 8 and 11, pick up size 11s (minus one now), and feed through the the main ring - these dangles will be separate from each other, so you do not feed the thread back through the last row of 11s.
and here is the finished product:
Obviously you can play with the colours, the accents, what kind of crystals you want, how long you want the rows to each be.
However, especially depending on the size of the holes in the beads in the collar, and the size of thread and needle you do, you will be limited in the overall number of rows you do. I think I managed 4 rows on these babies before I was running the risk of snapping the needle pushing it through the collar.
Also, too many rows and the top starts pushing up too much and it doesn't sit nicely on the top of the ornament.
Remember, it is a topper - there is nothing to secure it to the top of the ball yet - so you may want to use a dab or so of a good glue that dries transparent to the base ring to hold it to the hanger or ball.
Tell me if this needs clarification.