1.Login to your blogger dashboard--> layout- -> Edit HTML
2.Scroll down to where you see ]]></b:skin> tag.
3.Copy below code and paste it just before ]]></b:skin> tag.
img {
border: 15px solid #000;
background: #000;
filter:alpha(opacity=60);
opacity:0.6;
padding: 1px;
}
4.Now save your template and you are done.