To display an image in an Emacs buffer, you must first create an image
descriptor, then use it as a display specifier in the
property of text that is displayed (see Display Property).
Emacs is usually able to display images when it is run on a
graphical terminal. Images cannot be displayed in a text terminal, on
certain graphical terminals that lack the support for this, or if
Emacs is compiled without image support. You can use the function
display-images-p to determine if images can in principle be
displayed (see Display Feature Testing).