Hi A.Samarian,
Skins are kept in 2 locations
1. Data/skins
and also under
2. Data/Sites[SiteID]/skins
The site will always use the ones under Data/Sites/[SiteID]skins
When a new site is created a new folder is created, for example
Data/Sites/2/skins will be created if a new site is added and the files will be copied from Data/skins
So Data/skins is a library of skins to include when creating new sites.
Hope it helps,
Joe