FLEXIcontent outputs (joomla) template overridable images, by using
echo JHTML::_('image.site', 'myimage.png',FLEXI_ICONPATH);
Read joomla docs here
This means that:
-- IF there is a template myimage.png found back at "/templates/joomla template folder/images", use this one
-- IF NOT use the one in "/images/M_images".
image file names to use you can see if you do "view page source" in your browser.
e.g.
-- emain button: emailButton.png
-- print button: printButton.png
-- feeds icon: livemarks.png
-- pdf button (J1.5only): pdf_button.png|
-- edit button: edit.png
-- add button: add.png
-- approval button: person2_f2.png
-- favourites delete: heart_delete.png
-- favourites add: heart_add.png
-- favourites login required: heart_login.png