This is an open stitch that is perfect for the wonderful snow shading. The light blue or gray shading will show through beautifully with this stitch. Consider using a clear bead, such as Sundance Beads color 131, for the accent. Frankly, I would use a light sheen Metallic, such as Flair, Frosty Rays, or Crystal Braid, for the diamond itself.
I'm including a couple of variations to (hopefully) inspire you. The first adds an Upright Cross stitch to the center of the diamond. I strongly recommend using two different metallics, one for the Upright Cross and one for the Diamond.
The last variation leaves the center clear but fills in the diagonal stitch between the diamonds.
It's all a matter of taste. And your taste is perfect.
These stitch diagrams, along with all other #whimsicalwednesday and #smallspacesunday stitch diagrams, can also be found on a Pinterest board here.
If you like what you see on this blog, want to learn some very creative decorative stitches, and how to put them all together, whimsicalstitch.com sells stitch guides for seasonal Melissa Shirley designs. 27 guides are currently available and more are in the pipeline.