Two of these are derived from designs by Jerom (CC-BY): https://opengameart.org/content/retro-spaceships

One is based on a design by helpcomputer (CC-BY): https://opengameart.org/content/shoot-em-up-enemies

One is based on some pixels from surt (CC0): https://opengameart.org/content/astrominer-sprites

Earlier enemy sprites in this series: https://opengameart.org/content/super-dead-gunner-batch-2

Lots more in the series from my profile.