The Pixy Downloads - Free Stuff for design lovers - Download free psd, icons, mockups, patterns & backgrounds.

They is a lot of curated content here like a '150 image pack' with public domain images in, the ony catch is to unlock the download you either need to tweet or like the page on facebook to unlock the download. This is not the worst thing i have seen but it requires you to have one of those social media accounts.

Licenses will vary but should mostly be CC or PD.