Styling images is very similar to styling text. Their syntax takes the same format. However, even though all image properties also apply to text, some text properties, like color and font-family, do not apply to image properties.
Styling images' borders is very common. There are many border properties you can use. For example, border-width controls the thickness of the border, border-style determines whether it is solid or dashed, border-color determines its color, and border-radius determines how round its corners are. Here's an example:
This code yields the following result:
Again, there are lots of other image properties that you can use. There is opacity, which controls the lighting of the image, there's margin to control how far the image is from other elements, and width and height can also be used for them. More ways to style can be found at w3schools.com.