It is possible to update the kernel to the most recent backports version during installation.
Proceed with an expert installation all the way through configuring the package manager, and ensure the Backports option is selected.
Switch to the console (Alt-F2), and chroot into the installation:
mount --rbind /dev/ /target/dev/
mount --rbind /run/ /target/run/
mount --rbind /sys/ /target/sys/
mount -t proc proc /target/proc/
chroot /target/ /bin/bash
Then install the backports kernel:
apt-get update
apt-get -t jessie-backports install linux-image-amd64
It should be possible to upgrade almost anything from BPO this way, but I thought it better to save that until the first boot.