I've been playing around with this lately and it produces some pretty cool results at times.
The Deep Dream Generator takes two inputs , the first being the image you want to change and the second being the style you want the first image to be in. So it will "paint" the first image in the style of the second. For example :
The above image was generated from one of my photos (below).
And using the following image as the style.
Which I think came out pretty good :)
It has a heap of different styles you can choose from , or you can upload your own.
You can check it out here and have a go yourself.