Lots of patterns would do the job, but to me, it is the fabric that is going to make it "dreamy and feminine".
Pastels, lace, and embroidery are what comes to my mind when I think "dreamy and feminine".
Also plain fabric, blenders or small prints.
You might have a challenge to find blues, teals and purples in pastels, but they are out there.
There are some beautiful embroidered yardages that can be found too.
Lace can be mixed into a quilt, or used as a ruffly trim.
What about lace overlay on blues, teals and purples?
That could soften the look of what could become quite heavy and not so "dreamy and feminine".