Great names! I have to say my fav is Imogen Rose as it has such a nice sound to it But the name Allegra is so unique - gorgeous!

Some others are:
acacia, camellia, dahlia, daisy, fuchsia, garland, gem, geranium, heather, hibiscus, indigo, iris, jasmine, lilac, lily, magnolia, oleander, poppy, tulip, viola, violet, wisteria.