Manually adding thumbs not loading image

[lyndonnixon]

Wikimedia images inserted automatically in the information card appear in the ET, e.g.

Centre Pompidou
http://de.wikipedia.org/wiki/Special%3AFilePath/Centre_Georges-Pompidou_2007.jpg

However URLs added manually to a property "thumb" don't load the images, e.g.

Musee du Louvre
http://commons.wikimedia.org/wiki/Special:FilePath/Le_Louvre_-_Aile_Richelieu.jpg?width=300

(this is the URL visible in the DBPedia page. removing the suffix '?width=300' or replacing the colon : with the special character %3A also has not fixed it)