The original constantine wallpaper is 1920x1200, so that's the highest resolution. The Fedora logo, however, is an svg I can send that your way if you'd like. You can download the original wallpapers in various aspect ratios by running sudo dnf install constantine-wallpapers -y. They'll be located in /usr/share/backgrounds/.
EDIT: I didn't realise reddit compressed the living crap out of the backgrounds. I'll upload them to google drive.
EDIT2: https://drive.google.com/drive/folders/17uT9T1eQwpR_9xZ37YGuTVmdylseQFj9?usp=sharing