If you host your gifs and pngs using the picture uploader on Blogger, be sure to set your image background to transparent. Otherwise your images, signatures, etc will have a background , border and/ or shadow around them. Set border around images to transparent as well in your template.
You will have to go inside the html template to remove shadows,etc from them if you don't find it on the template "Customize". Always , always save your blog first before you change anything!
Once you find the shadow and moz opacity, just set all the numbers to zero.
You will see something that looks like this:
This is what controls your image shadow on the blog. If you set a background, all images will have a background.
My images are set to have no background and no border and no shadow.
Set all the numbers to zero and you will remove the shadow. NOTE: You dont have to go inside the template if you can access the shadow through customize!
The higher the last (4th from left) number, the darker the shadow around your photos and images.
If you have no background set for your images and still get a background, then you will have to host them elsewhere like Photobucket or Image Shack.