A couple of the computers I use have limited RAM (4 GiB), and Chrome and Firefox use up a lot of memory. So, sometimes I don't want to fire up an entire separate web browser, and since I'm almost always in Emacs anyway, I just use the Emacs Web Wowser, the web browser written in Emacs Lisp.
Here are the functions I use to switch Emacs to using EWW by default to open URLs:
(defun tkb-browse-url-eww (url &optional args)
"Invoke the eww browser (inside emacs) on URL. It the optional second
argument ARGS is true open in a new buffer."
(message "args: %S" args)
(eww url (and args 4)))
(defun tkb-toggle-eww ()
(interactive)
(cond ((eq browse-url-browser-function 'browse-url-default-browser)
(message "Switching to EWW for opening URLs.")
(setq browse-url-browser-function #'tkb-browse-url-eww))
(t
(message "Switching to browser-url-default-browser for opening URLs.")
(setq browse-url-browser-function #'browse-url-default-browser))))
You could do something similar using w3m.el, which uses the external text mode web browser w3m to render the HTML, but that doesn't (as far as I know) support images, and EWW does.