Shouldnt this have been .png instead of .gif?
According to the Data Table, Its asking for .png file name and I dont quite remember how to change it to the correct file type.
In templates such as these, the default supported file type is png, you can change this to gif adding |Ext=gif to the template.
I have added this for now, but it is prefered to have the actual in-game icon of the item (in png format) wherever possible.
Changing the extension of a file already on the Wiki is not possible, you'd just have to upload the other type and it will work fine.