The Morrison Garden Perennial Bed: It looks prety good to me; maybe a little structure and a little "POP"

I've been charged with doing a little redesign of this bed. Actually, I'm flattered at the idea that I could make it better. Originally there was a drift of roses center left mid-ground, that provided a little structure and slowed your eyes down. They didn't prove to be as disease resistant as claimed so they came out and now beautiful chaos reigns. The dominant plants now are orange Echeverias and blue Nepetas which is good; the original color scheme was orange and blue. Flowering now are orange Galliardias, Lilies, Red-Hot Pokers, and blue Camassias, Verbenas, and Geraniums.

I'd like to add some larger plants, as most of the surviving selections are nearly the same height. I love Rosa 'Mutabilis', and we have an extra plant in China Valley. It'll look good slightly off center left towards the back of the planting. It is disease resistant, will flower all summer, is fragrant, will fit with the color scheme, and can get 6 feet tall and 8 feet across in two years.Vernonia novaboracensis in the back left for fall purple, Helianthus angustifolius back right for fall yellow. A grouping of Canna 'Prretoria' on the left side and two individual plants middle and right to form a loose scalene triangle. Monocots can add structure, boldly-textured ones even more so. I'm thinking about a giant grass in the back, maybe Arundo donax variegata. There's that new cultivar that supposedly doesn't viridesce. The Cannas will add pop. Maybe Canna 'Australia' against the left wall towards the back? I don't know about introducing black but I love that foliage! Consolidate the Camassias and move them center-right to the left of the sign. Move some Echinaeas from right to left to balance the masses a little. Keep the spectacular threads of Nepeta. I'm even thinking of adding a Musa 'Basjoo' along the right side wall towards the back. An 18 foot banana would get peoples attention, add some "pop"!

This is going to be fun.