Have you read the manual?
1) If you are using the Apple provided rsync then use the -avE options
2) add --exclude=Icon?
3) add--exclude=Icon? --exclude=.DS_Store remove the E option
create an empty Icon? file->
In the second case, namely sync from the first folder all except to the icon of the principal folder, but including icons....
That is not what you originally asked for. You need to read the manual. If you want the principal folder copied to the destination folder then you need to leave off the trailing "/" from both path arguments. The following is untested, use at your own risk, but should do what you are asking for now.
rsync -avE --exclude="$1/Icon?" "$1" "$2"