as of now webi templete is based on the some webi query.like create webi templete on the efashion universe.temple is based on the some source.with this you have to add the webi query in the existing templete and need to delete the query from the the report which is used for the templete.
in the idea it is considered for future enhancement.
CSS custom file is available from BI 4.0.based on the need you can create your own style.