I am not sure, but I think that the fonts that the skin uses need to be defined in the file "fonts.xml", which can be found in the folder for the skin that you are using. Find that file and check if there is an entry for "font16". If there is not, copy one of the existing entries, and modify it appropriately (e.g. copy the entry for "font15" and change the name to "font16" and the height to "16").GUIFontManager: Font with the name 'font16' does not exist