As you probably know, WorkShelf is in constant evolution, with new modules and features being added as time goes by. That means some of those themes came out before there even was a RAM Meter module.
When a theme does not have bitmaps for one of the new modules, WorkShelf automatically applies a
generic background to it (which actually is the bitmap used in NextSTART for task tiles), so that the module blends in with the rest of the theme.
In order to use all the advanced skinning options for modules that are not being skinned by a particular theme, you will have to add the relevant bitmaps yourself... which means you will have to learn how to skin WorkShelf.
As for not being notified by email when replies are posted, maybe it was because you forgot to log in in your reply prior to this one? You posted the reply as a Guest user.