Here are some links of quilts I have done that might give you some ideas.
On this quilt I put a motif in the corner
Mariner's compass sneak peek on my LA
ON this quilt, scroll to the 3rd and 4th pic. I sprayed out in the corners and had the feathers circle back on themselves in the centers of the borders
Hand pieced quilt quilted by Feline Fanatic
On this quilt I did turn the corner but still had the feathers meet in the center because the plumes changed directions (2nd pic shows the turning the corner)
Farmer's Wife Sampler (FWS) Quilted by Feline Fanatic
This one I did the same thing:
Feathers and hearts and diamonds baby quilt
I always mark my spines and I drew a lot of feathers and experimented on paper with what worked best for me.