I did a Dresden Plate appliqued randomly onto one large background fabric as you inquired about. And I have to agree with much of what Prism99 said.
Before appliquing a plate, I heavily starched the background fabric in that area, and I also used a lightweight two-sided fusible tape (just around the edges of the plate) to afix the plate to the background, as well as pins.
Manuvering the bulk of the quilt while sewing down the plate was combersome, but do-able.
I even included a few half plates around the edges of the quilt and quarter plates in the corners. I haven't quilted it yet, and will most likely send this one out to be done on a long arm instead of trying to FMQ myself.
Sorry the picture quality isn't so good, I had to pull the quilt off the shelf to take the pictures, and didnt' take the time to iron out the fold creases.[ATTACH=CONFIG]555353[/ATTACH]