Use thumbnails for files (mp3, swf,..)

1. Go to Dashboard
2. Go to Sitewide Settings > attribute : In the 'Image/File' row, make sure there is a tick in the "file" column. If there is no tick, add one and click SAVE.
3. Go to File Manager > Attributes and create a new Image/File attribute. 
4. Enter "custom_thumbnail" as the handle, and whatever you want for title.
5. Save It
6. The attribute has been created! Now you need to associate the file :
7. Go to File manager
8. Pick an swf or mp3 file and select 'properties'
9. The attribute name that you created should appear at the bottom of the list.
10. Click on it and choose a file.
11. Click on the pencil/pad icon at the end of the row to save your choice.
12. Your file will now show with your thumbnail in multimedia box.