I have not said anything the last time since i assumed that the painting was old (checked that just now, that painting is definitely free to use), but this time, with the new project, it looked to young to be copyright free.
I traced the image back to a Russian site and a deviant art account.
I can not confirm this for the Russian site, but as fare as deviant art is concerned, that picture is not listed under Creative Commons 3.0 or Public Domain.
Please check the copyright status of your used images (if you ever wondered why i don't use images, this is a hornets nest that you don't want to have in your living room).