There are many that fit both categories in this regard, ¿unfortunately?, due to the number of them that are edits from IntSys’ art. While most of the full custom animations have arguments for saying they’re totally usable elsewhere, plenty of them are borrowing their choreography, visual appearance, or otherwise from some specific thing.
While the intention is for these to go into FE fangames, I highly doubt anyone would be upset about using them otherwise; but I would highly recommend asking the artists if possible about using their work just to cover your bases if nothing else.
Cam beat me and better-posted about what else I had to say here.
There have been a number of commissionable artists who even do battle animations and plenty who like to do animations for fun - Quite a few of Dark Deity’s combat animations got done by animators from this community, for example.