When you add a image to the description of an external tool (mod_lti) and set 'Display Activity description when launched' to on, when viewing the actual activity the href's for the images are emitted as:

http://wwwroot/mod/lti/@@PLUGINFILE@@/DSCN8289.JPG

Appears the intro text is not being run through the standard function used to transform those magic placeholders (@@PLUGINFILE@@).

Replication steps:

1. Click 'Add an activity or resource' from the course page
2. Choose ‘External tool’ and click add
3. Enter an Activity Name
4. Click "Show more..." to expand the advanced settings
5. Edit the Activity Description and insert an image an emoticon using the editor’s functionality.
6. Check 'Display description on course page'
7. Check 'Display Activity description when launched'.
8. Click Save and Display
9. Return to the course page

Expected: You can see the image you uploaded when the activity is displayed and on the course page.

Actual: The image displays on the course page, but when viewing the activity itself, you see no image and your browser inspector will show that it tried to load a url with @@PLUGINFILE@@ in it.