Grass & Flower Combinations

I have planted low-growing grasses in small, square beds and think they will need some taller, wavy flowers planted amongst them. But which flowers? I have combined Luzula Nivea and Carex ‘Frosted Curls’ and I think blue flowers would look good standing above the grasses, and perhaps the cornflowers are best as this is a cottage garden.

Small globe thistle (www.crocus.co.uk)
Small globe thistle (www.crocus.co.uk)
Verbena Bonariensis 'Lollipop' (www.crocus.co.uk)
Verbena Bonariensis ‘Lollipop’ (www.crocus.co.uk)
Cornflowers (www.crocus.co.uk)
Cornflowers (www.crocus.co.uk)