All of my art with the Creative Commons license (see bottom right of the art page) may be used anywhere (YouTube, websites, blog, wallpaper, etc.) and may be modified as long as
You give credit to me (e.g. Image by HizkiFW)The license remains Creative Commons (you can't copyright it)You don't use it for commercial purposes Read more here.
All other copyrighted work may not be used anywhere other than for personal use (e.g. phone/computer wallpaper).
If you have any questions, feel free to ask in the comments below.