Euphorbia are a wide range of plants many of which are suitable for flower arranging where the bracts and leaves both add interest.

Pittosporum tenuifolium can be used for flower arranging to good effect due to the dense nature of the crinkly edged leaves on dark stems. grow in sheltered locations to get plenty of useful foliage.

Fatsia Japonica or Fig leaf palm is a shapely leaf for Flower Arranging. Also sold as Aralia Japonica, the bold shiny leaves work well in traditional flower arrangements

Corkscrew Hazel and Contorted Willow are both twigs that add movement and style when flower arranging. Mix with just one type of flower as less is generally more with Hazels and Willows.

Phormium or New Zealand Flax is an evergreen, clump forming, hardy perennial. with long strap shaped leaves that add height and formal style to a flower arrangement

For a cast Iron winner in the flower arranging stakes you could do a lot worse than use Aspidistra leaves aka the Cast Iron plant. Slow growing so you may wish to buy your leaves but after glycerine they will last for years