Check both the Resources and Creative categories. Many users make posts compiling their work, often with some of them marked F2U. As a example, here is mine: Construction Yard of Norikins
There are several reasons why not all F2U stuff is on the repo. They may not want it on the repo, and want to be the sole distributor. The repo maintainers may have failed to add it and it slipped through the cracks. They could be an old user who left before the repo existed and could never grant permission.
Outside of here there are a few very old FE sprites on DeviantArt the description says you can “use with credit.” Though they are nearly never formatted.