Hello guys,
We just released a new blog post listing 20+ places to get game assets. The list is ordered from free to free/paid (a lot of sites have some freebies for you to try out before you buy something from them). Of course, while free assets are a great, inexpensive way to try out your game's idea, it's worth investing into paid assets or hiring on an artist when you've got the funding for it.
Hope this helps you devs who are missing certain assets or are looking to make a demo to validate your idea!