If you hadn't seen on the discord, but I had some disagreements with categorizing splash arts to a specific nation, as some were hints but were not likely made with the nation in mind. I just took that I should ask now than later, especially after seeing the images you added to certain nations today. I am not aware if there is some discussion board atm about this, but I find adding some of the skins to given nations to be more speculated opinion than anywhere close to actual ties.
For example, I noticed today the Elderwood skins being added to Ionia, although Ionia is not about forest spirits and the likes. Surely, as of recent it has been the hotspot of magic, but I wouldn't put a finger that those skins belong to Ionia, or any other nation, for now. This is rather obvious with how Emerald Taric has no semblence of Ionia in his look and art (he's much more an elf, which I wouldn't entitle as Ionian).
The same can be said for the music: I can understand having Rhaast's login theme in the Noxian page (not because of the music, but because of who appears in that page; otherwise, I would pin this to the Darkin's page instead), but not Kayn's. While RITO has made distinct musical choices of what each nation will be represented by, I wouldn't go any further than tagging music to their designated champion, thus which nation/area they are from.
Thank you very much for reading, and hope to hear from you soon. If discord is better to chat about this, please let me know.