Not a lot of room, How about a sculptural euphorbia, because you are going to want something that's contained in shape (not bushy) and makes a statement like an art pc. Not too green tho.

Ask your family what they would like to see, not designwise, but plant materialwise - color, texture, fragrance. Even ask your mother-in-law. You have provided some architect's dream, with the bold geometric forms, the bold palms and cycads. How about something warm and fuzzy. Something to rub your hands on as you head to the door. Some color and fragrance beyond the white and palm trunks. How about vines to soften the hard edges of the planters, fill them with ground cover plants so you won't see the mulch in a couple years, add bulbs of all seasons to bring cheer, glossy leaves to brighten your day. Bring nature to your entrance area to warm up the arrival of your mother-in-law. How about saving room for a couple chairs and small table, to sit out and prove that people actually live in this piece of marvelous sculpture, and add the warmth of an outdoor room. Spend some time at the library with books about the architecture of Frank Lloyd Wright. He is the one who introduced the architectural design idea of the outdoor room. Come to think of it, I don't remember ever seeing a garage door in any of the photos. Guess I'll have to take another look.

I have lots of these at my place, very hardy!! Give them some initial love and they will return it for a lifetime. I have also broken off a few of the end pieces from time to time (once it is doing well) and have placed them in water - my oldest one is going on a year in the water alone!

Hi Brett, this is an image from Outdoor Establishments in Sydney, one of their Mosman projects. Maybe you can ask them? I'm tipping Dianella or possibly Liriope. Leaf blade is too wide to be one of the more likely Lomandra's.