Something that could help is a dark center instead of the same color as the background.
As for the plate edges I would use a fusable webbing like wonder under or something like it to fuse it to your background then finish it with either a decrotive stitch by hand or your machine. I would not use Ricrac it would take away from your very pretty blades and be very difficult and bulky since it is not a biased product it will not bend and turn smoothly. If you really want to cover the plate edge how about a cording instead.