You may have turned off "Show Images" in your browser, check in the browser settings.
Also check if you are running any extensions that can block parts of webpages, such as Adblock Plus, Ghostery, uBlock Origin etc, these will show as small icons in the top right of the browser, on the same line as the adress bar.
If you are still stuck, reply with which browser you are using (and version of Windows) I can help you further.