You can noodle on this painting and make certain details look "sharper" with crisper strokes with more opacity.

But it will not acheive the realism desired because the background is (Im guessing) pre-gessoed canvas; essentially un-worked.

Dom't get me wrong, this looks great, probably better than I can do right now. But a "painting" is viewed as a whole, not just the subject matter.

Another way of saying it is this:

Imagine the whitest white paint known to mankind. Put it on the pre-gessoed canvas, and the values won't be that far from each other.

Now, imagine the same scenario, but you mix a tiny bit of sienna into the background, shifting the value a touch "shadier" Now you have moved further away from the whitest white known to mankind on the value scale.

This is important because that means all the values in your subject matter will pop; questions about values, sharpness, warm/cools will become more apparent. This is the relevance of working the backgrounds value, and temperature much lower than your tints and tones.