I like sunsets.

Usually images of natural landscapes relax the mind and help distract oneself from his/her thoughts. In my opinion, the more detailed the picture is, the more time the mind spends on processing it and uses the imagination to place you in the picture virtually.

A quick search in google provided some results that might offer some useful suggestions:
http://www.allp…
http://www.worl…

It depends on individuals. Some people are influenced by arts and quotations. They get inspiration seeing them and it has a positive effect on them. But some others think it is a load of bullshit and don't bother to have any. There are others who think it will be beneficial because all other do so and put something in front of them but get bored seeing the same everyday. You have to ask yourself which type you belong to and decide.