Found this Stock Image of Cork.
The author at Deviantart says:

You have the permission to use this image in your digital art, on other websites, projects and prints as long as it is altered in some way (such as using it with a drawing/text overlay, digital art collage, backgrounds, texture etc.) Basically the only thing I don't want is the exact same image to be sold or uploaded in other stock/texture galleries.

http://enchantedgal-stock.deviantart.com/art/Corkboard-Wood-Cork-Composite-49823242

Chris, thanks a lot for the link! I ended up finding a bunch of other texture which I'll probably experiment:

http://enchantedgal-stock.deviantart.com/art/Opal-Metallic-Paper-Stock-47678085?q=gallery%3Aenchantedgal-stock%2F19558821&qo=8
http://enchantedgal-stock.deviantart.com/art/Swirl-Pearl-Texture-Stock-48256591?q=gallery%3Aenchantedgal-stock%2F19558821&qo=35
http://enchantedgal-stock.deviantart.com/art/Gold-Metal-Wood-Pattern-Stock-48247186?q=gallery%3Aenchantedgal-stock%2F19558821&qo=30
http://enchantedgal-stock.deviantart.com/art/Silver-Wood-Stock-Texture-48247039?q=gallery%3Aenchantedgal-stock%2F19558821&qo=29
http://enchantedgal-stock.deviantart.com/art/Blue-Jean-Clothing-Texture-48594008?q=gallery%3Aenchantedgal-stock%2F19558821&qo=43
http://enchantedgal-stock.deviantart.com/art/Tan-Carpet-Fabric-Texture-48682020?q=gallery%3Aenchantedgal-stock%2F19558821&qo=45
http://enchantedgal-stock.deviantart.com/art/Tan-Carpet-Fabric-Texture-48682020?q=gallery%3Aenchantedgal-stock%2F19558821&qo=45
http://enchantedgal-stock.deviantart.com/art/Cardboard-Brown-Paper-Texture-49218463?q=gallery%3Aenchantedgal-stock%2F19558821&qo=58
http://enchantedgal-stock.deviantart.com/art/Corkboard-Wood-Cork-Composite-49823242?q=gallery%3Aenchantedgal-stock%2F19558821&qo=79

Fixed in master (054ece6c99840027147d34175d14819275eb445b)