Skinning for OpenPHT (and Kodi) can be a little strange -- things that look hard can sometimes be very easy and many times things that look small and simple involve a fair amount of code to change.
Adding viewtypes to media that don't already have that viewtype falls into the "harder than it looks" category. For most of the viewtypes for the different media types they support it is different (but similar) code that renders the viewtype for the different media types. So unfortunately, I cannot point you to one or two lines of code to insert an existing viewtype into a different media section -- because actually what needs to be done is a rewrite of the viewtype -- made specifically for the new media type.
That's the bad news. The good news is that I have the next 6 months of coding for Nox (I work on it every day) planned out and adding viewtypes that are missing in certain media sections is already on the list (when appropriate of course, there are some that are ill suited, or flat out impossible for some media -- like trying to use BannerInfo for movies, no movie banners supported by PMS, so that view would be all kinds of messed up in any section other than TV Series). Over the next few months I will be updating the viewtypes one-by-one adding new features to each. I've already started work on the first one List Viewtype (which surprisingly, code-wise, is one of the most complicated of the viewtypes, despite its simple appearance), and will be doing the rest in order (the order that they appear in the skin's xml folder) -- which means Showcase will be the forth one to be done.