There are databases available,
hyperspin in .xml (but no synopsis) and GameEX if I remember correctly in .mdb (synopsis etc...).
Creating database for Wiiflow with this should be feasible.
I don't care much about banners in fact, except per plugin that may be nice.
Regarding the last request, it's not exactly what I meant. Sorry but I'll quote myself:
Would it be possible to have an option to go to a specific category when you choose a plugin in source menu? For example, if we want all mario games in existence from all machines, we could create a category "mario", combine the related plugins, and then have access to the games directly from source menu.
If none of this is possible, no problem.
Maybe a bit upset though...