Yucca filamentosa 'Color Guard'. Plenty other yucca, aloe and agave choices where you are. That is a good texture and color contrast.

Pick plants that will enjoy the same growing conditions - ceanothus, kniphofia, rockrose (Cistus sp.), leptospermum, yucca, agave or other succulents, lantana, kangaroo paws (Anigozanthus), gazania, lavender.

Most ornamental grasses work well also.

And I think you mean mugo pine :-)

@gardengal48 (PNW Z8/9) Thanks - yes - mugo

I just got a Yucca filamentosa . Its a beauty! It takes on pink tones in the winter.

Succulents are so architectural and make such a strong statement that you should look for some contrast -- plants that are soft, loose and feathery.

You're rights thinking about grasses. My favorite is Mexican feather grass. It stays soft and light all year round and never gets that dried up, stiff look like other ornamental grasses. It also stays under 2 feet.

Globe mallow "Louis Hamilton" pairs great with succulents. It may look a bit floppy at the nursery (all that water and fertilizer) but will improve after pruning. The foliage is bluish and the blooms are bright coral. Mine have been in bloom since October, and the main spring flush is still a couple of weeks away!

Also, consider the dalea family. Black dalea (Sierra Negra) or gold (Sierra Gold). Small flowers but showy when in full bloom. They are stunning with agaves, but should work with a prickly pear.

Be careful where you plant Mexican feather grass, Nassella tenuissima. It self sows with abandon and is considered an emerging invasive species along much of the west coast, California especially. (It is a weedy pest here in WA state and currently on the "watch list')

I'd plant a gray/bluish agave nearby. Something like Agave ovatifolia. Gorgeous plants! Or, maybe a variegated agave of some kind -- like Agave lophanta Quadricolor. Something lower and mounding in form. How tall is your Opuntia? Got a pic? Are you able to remove weeds around these plants? Is it in a gravel bed?