Today we know about 

CSS Styling Images

first we know that (Use the border-radius property to create rounded images)

First EXP:::

img {
  border-radius: 8px;} 

And we convert this in new style 

Type next 

img {

  border-radius: 50%;}

this tag is for convert pic in cicle 

Next we convert img in thumbnail

Use the border property to create thumbnail images.

So  type 

img {

  border: 1px solid #ddd;
  border-radius: 4px;
  padding: 5px;
  width: 150px;}

<img src="img.jpg" alt="my">

Here we see that img has converted in thumbnail

If you to add link in this pic/img so simple type 

img {
  border: 1px solid #ddd;
  border-radius: 4px;
  padding: 5px;
  width: 150px;}

img:hover {
  box-shadow: 0 0 2px 1px rgba(0, 140, 186, 0.5);}

<a href="Link">
  <img src="paris.jpg" alt="Paris">
</a>