Most, of the provided droplet images have GPT volume headers, a single partition, and use grub as their booloader. Grub isn't happy with this: it expects a bios_grub flagged GPT partition to write its bootcode to. The two proper alternatives are:
1. GPT header, tiny vda1 with bios_grub flag, vda2 with ext4 rootfs
2. MSDOS header, empty sectors until 2048, vda1 with ext4 rootfs
While this compliance may seem pedantic, it is having a real effect on some automation scripts I'm running, which depend on grub2-install running without --force to force a blocklists installation. I'm not asking you to fix all the existing images, but maybe moving forward we could get images that conform to one of the two layouts described above?
Fedora 24 x64 was the only actual image that I found that was compliant with #2, above.