Honestly, I don't have any idea, too D: I have like thousands of textures (no kidding) and this came out on a "15 minutes of doing whatever you feel like" in Photoshop. I saved a lot of tumblr edits on my inspiration folder, but this has nothing to do with the epic graphics I saved xD But I guess it's practice and getting used to this Tumblr style.
You can check my "textures" folder here on my favourites. Most of the textures I use are there. Also, check tumblrs like its-photoshop, pscs5, yeah-ps and such. There are a lot of tumblrs that reblog any type of resources! Checking the texture pack and textures tags could work, but it will take longer.