Fedora 26 is released today. virt-builder images are already available for almost all architectures:
$ virt-builder -l | grep fedora-26 fedora-26 aarch64 Fedora® 26 Server (aarch64) fedora-26 armv7l Fedora® 26 Server (armv7l) fedora-26 i686 Fedora® 26 Server (i686) fedora-26 ppc64 Fedora® 26 Server (ppc64) fedora-26 ppc64le Fedora® 26 Server (ppc64le) fedora-26 x86_64 Fedora® 26 Server
For example:
$ virt-builder fedora-26 $ qemu-system-x86_64 -machine accel=kvm:tcg -cpu host -m 2048 \ -drive file=fedora-26.img,format=raw,if=virtio
Why not s390x? That’s because qemu doesn’t yet emulate enough of the s390x instruction set / architecture so that we can run Fedora under TCG emulation.