I like to add images to my blog design and blog posts. I just do not always like the shadow around the pictures. I am guessing that the shadow box is simply a default on blogger. As you can see, I changed the colors of my blog design because the blue background image that I had seemed to break down on my browser. For some reason there were white horizontal spaces on the screen while my page was downloading.
This is the old design.
With this new design, I decided to add the cute apples on my sidebar to match the red background. I did not like the shadow around the image. It just does not make my blog look clean. I was about to consider using this custom blog design in Florida but then I searched for a solution. I found an article on sillygrrl.com. She has two simple ways to do this. I tried the first option where you add some CSS to your Advanced tab under Template designer. This did not work for me. Then, I tried the second option. I had to go into my html to delete 3 lines. That option worked nicely.
Here is the link if you need to remove the shadow box from your images.
http://sillygrrl.com/2011/07/30/how-to-remove-image-shadows-in-blogger/
Good Luck!