Here are some of the more unusual things you can do with PhotoShop. For example, here is a photo I took of Trafalgar Square turned inside out:
Or maybe, the other way around?
How about some pop art:
Here is some selective colouring on a black and white photo:
And again with water in motion:
Waltham Abbey in canvas water colour. This was not just a filter, but many layers of painting/contrast:
Waltham Abbey Church