8.3 Use Appropriately Sized Images

It is important to size any images appropriately for their use when shown directly on the page or stored in the database.

If you only need to show thumbnail sized images on your Web Page then the accompanying image files should have appropriate proportions (and size).

There are lots of tricks which can be used to make your image files smaller:

Reduce the image dimensions

Reduce the image quality

Optimize Images for the Web

Blur unimportant parts of the image

Use appropriate file types

Look online for more information on this topic (it's a big one) and check out Displaying Images.