(img) Took a quick shot at identifying the regions.
The only ones I know for certain are free to use are the vanilla portraits, which you can find in completion here (https://cdn.discordapp.com/attachments/206588291053649921/423956771845963786/p.png).
Not sure the license on Nickt’s Radiant Collection, since it doesn’t show up on his thread. (He does have a big F2U collection worth checking out, as does Laurent.)
As for the rest I’d say please leave them alone.
If you need mugs, there are plenty of F2U collections:
Mug Blitz 1 2 3 4 5 6 7
Ultimate Graphics Repo
Communal Portrait Collection
FE6 Blinks
And some spriters release certain mugs as F2U on their threads.