org-agenda-category-icon-alist

org-agenda-category-icon-alist is a variable defined in `org-agenda.el'.
Its value is

nil

Documentation:
Alist of category icon to be displayed in agenda views.

Each entry should have the following format:

(CATEGORY-REGEXP FILE-OR-DATA TYPE DATA-P PROPS)

Where CATEGORY-REGEXP is a regexp matching the categories where
the icon should be displayed.
FILE-OR-DATA either a file path or a string containing image data.

The other fields can be omitted safely if not needed:
TYPE indicates the image type.
DATA-P is a boolean indicating whether the FILE-OR-DATA string is
image data.
PROPS are additional image attributes to assign to the image,
like, e.g. `:ascent center'.

("Org" "/path/to/icon.png" nil nil :ascent center)

If you want to set the display properties yourself, just put a
list as second element:

(CATEGORY-REGEXP (MY PROPERTY LIST))

For example, to display a 16px horizontal space for Emacs
category, you can use:

("Emacs" '(space . (:width (16))))

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.