Board Thread:Off-topic Discussion/@comment-27713488-20171119055244/@comment-27713488-20180212010845

I disagree. A thumbnail of the map is useless anyway, and the other reasons PNG is better still stand, especially when small details on the map may be important and should be protected from JPEG artifact corruption. Also, your JPEG's file size is nearly 50% larger.

I will ask the support forums and contact Wikia staff if they cannot help, but if nothing can be done I still do not think it is good to use JPEG in this case.