never really seen a guild emblem with transparency.
Actually the best way would be to rename the extension from jpg to png
Cause most uploader detects just the extensions.
Changing the header to jpg would be allowing the image to go through and hopefully the image will be decoded as png
Or try double extensions
KURAN guild their emblem has transparency.
<-got file from C:\Chinesegamer\LuniaTW\GuildMark\41433.jpg
i think that they used the changing the header method. wouldnt the original emblem have to be png for transparency becuase jpg does not support it.