About the shading, you should go even darker. I notice that you use mostly very bright colors. If you are to apply a black and white filter, the colors you use will fall into the White - 50% gray range. Without using the other half, 50% gray - Black, your pictures won't have enough contrast for things to stand out. For example, that pearl almost blends into the upper half of the shell. The pearl itself also needs a bigger range of values for the "shine" to be more noticeable.
Let me just make a quick example:
(that shine I made is far from enough contrast, but it's just a sample, so...)
Same goes for the rose. Those nooks between the petals? Make them darker. Night scene? Also darker.
One thing to note though, avoid using pure black and pure white. Pure white is only for "shine" on really shiny things such as metal or eyes. Pure black... I can't think of any use for it. Dark alley at night maybe.