[Milhouse]

but it does limit the max cached image size to the gui resolution (which perhaps it shouldn't).

My reason for whacking up the fanart and poster resolution is that I might be accessing the media library with a 1080p-capable tablet, and don't want to be faced with a tablet display full of horribly pixelated artwork (which certainly used to be the case with the default settings back in the day, but I notice 720 is now the default fanartres, although imageres is only 540).

When using a tablet to browse the library (and thus artwork), it doesn't seem appropriate to impose restrictions that are designed to optimise the performance of the Pi GUI display, which isn't being used...

So I would say "shouldn't", and let the user decide what works best for them and how they will be consuming the artwork.