It's amazing how a canvas design will come to life when the stitching begins! Even if I had painted the canvas first, the threads would liven it a lot.
Threads are just so much prettier than bare painted canvas, as the textures are what make the piece, as well as the colors. I think this is the main reason I'm not fond of the "light coverage" thing - I feel like "why bother to stitch it at all?"
However, in the opposite direction, I see entirely too many different threads, sometimes, used on one small piece, for no apparent reason. There should be a purpose for each thread chosen, so that the stitched design works as a whole and not just as a collection of different textures, which can become an eye shattering mess.
Petite Very Velvet may seem a strange fiber to use on a creature which lives in the water - but in this case, I wanted a coloful background for the sparkling, shiny, and gleaming accents on the fish. Then there is the fact that, worked in basketweave, the PVV has almost no texture or light refraction, so just looks like a smooth, soft area.
My first thought had been to use the DMC Satin Floss for it's shine - but realized that it would be so shiny and have so much "light break-up" on the surface, that it would detract from the "jewels" and other design features. I will use the Satin Floss in another place - but more logical than the background "skin" of the fish.
The jewels are worked in a "bump stitch" I enjoy using, and with Rainbow Gallery Flair, as I didn't want a lot of sparkle here either to compete with the metallic braid of the chain. The Flair has just enough sheen to look right.
Usually, I go about choosing the threads for a canvas with something in mind first, but then upon dumping out the various categories of stash threads, I will spot something better than what I had originally intended. More on this later, as I move along with the fish and begin on a shell.