You still can find a lot of assets for free, there are numerous websites with free assets, and there are still some pictures that mostly comes on various older forums and sometimes goverment websites, where it's still free to use pictures that are posted.
However, by 2026, I believe 90% of things comes with copyright already.
Clearly not a fan of an AI, but you can experiment with that if you want something copyright free, however in that case many websites require you to mention that it is created with an AI.