Take a look at these collections of beautiful hand drawn icons. And you can use them in your projects for free!
At Good Stuff No Nonsense they offer you these sets of icons under Creative Commons License CC BY 4.0. You can use the icons for both personal and commercial projects, just be sure to credit Good Stuff No Nonsense.
Icons are available in multiple graphic versions - outline, color and sticker. A must for every website developer and UX designer.
For example, here are some space icons for your next SciFi related project.
Disclaimer
I am in no way affiliated with the offer aboev. Call me a happy user, that's all :)