BC wrote on Apr 6^th, 2020 at 4:23pm:

EDIT: got the iniBuilds livery to work! It can be installed via the ACE, however, it does need a new thumbnail, as the included one is not an AA 772. The thumbnail on the inibuilds page can be used for that, once converted into a jpeg.

I downloaded, and added, the American Airlines 757-200 (N939UW) via ACE, and I didn't need to add a thumbnail.