Saw a great project on Serenes Forest but it looks like it was abandoned. I wasn’t sure if there were any other attempts that got finished and released publicly. I did find a couple on the mug contest threads but not very many. Thank you
If it’s just a mass recolor I think there are two versions floating around somewhere, buried in discord or a dropbox.
If it’s a dedicated upgrade (reshading to match FE8’s style on top of color matching), as far as I know no one’s completed the entire set and shown it off.
This one here is exactly what I’m looking for but it’s abandoned and was never released publicly. So something like this is really what I’m searching for. The Mugging blitz threads had a few here and there and the discord looked like it had a couple but no complete collections or anything. I feel as though only having half of the characters updated would be weird and jarring and look out of place. Do you know of any other places I can look?
I’m 90% sure there isn’t a publicly available collection of them all. As you already found, most have been made available through blitzes. You could take up the mantle and make some magic happen, though 
I just might, I’ll let you know if I do. So far all of my experience has been in weapon icons but the moment I learn the ins and outs of portraits I’ll give it a shot. It seems like it may be relatively simple.