Usage
#CHEMIN_IMAGE{article}
will return
prive/themes/spip/images/article-24.png
2nd example
[(#CHEMIN_IMAGE{cookie-32.png}|balise_img)]
will return
<img src="prive/themes/spip/images/cookie-32.png" alt="" width="32" height="32">>
As of SPIP 4.0 : The argument can be a PNG file name containing a specified size as suffix: for example #CHEMIN_IMAGE{forum-public-24.png}. 
In this case, if there is an SVG file in the path with the same name and size suffix (forum-public-24.svg) or with le suffix -xx polyvalent (forum-public-xx.svg) , the path to this SVG file is returned. 
This makes it possible to
-  to benefit from SVG icons in SPIP 4
-  to benefit from a simplified SVG icon for small sizes
-  to keep compatibility with SPIP 3 thanks to the PNG version.
Searched paths
The image file passed as an argument is searched:
-  priority in the image folders of the private and plugins: subfolders /prive/themes/spip/images. By default the theme is ’spip’, but it is possible to change the theme by setting the constant _SPIP_THEME_PRIVE.
-  and, otherwise, in the subdirectories  /images of the SPIP path and active plugins.  This ’images/’ sub-path can be modified by setting the constant _NOM_IMG_PACK in your options file.
See also
The filters