Ave and wassail,
That depends on the picture and the purpose. Most of the pics taken in-game are the property of the game developers, since it is their artwork. Those created by authors here have their own copyrights.
If the purpose is non-commercial (you are not using them to make money), then the general rule is to use them, but give credit to the source.
If the puropse is commercial (you will be making money) then you need permission from the game developers and/or the person who created the image you wish to use.
[This message has been edited by Terikel Grayhair (edited 04-02-2019 @ 12:39 PM).]