Ummm... being less than expert, I don't know many, but what about love-in-a-mist? We have it setting seed every year and I think it'd go with a soft look (of course , it also sets seed in the lawn every year too, so one has to watch it). Grape hyacinths are also lovely, and would suit a small garden maybe?

We have irises, blue, purple and white (plus one powder blue - we have no idea where it came from, it just appeared and grew like Topsy, but is very pretty).