To invert the layer:
Copy the layer
Cmd J
Click the 'normal' drop down menu and experiment with different settings
Above is an example of a picture I took in London that I manipulated in photoshop. I inverted the colour and selected the 'lighter colour' option in the drop down box.
To add a filter:
In photoshop click on the drop down menu for filter, then select filter gallery. This offers various filter options. Many of which can distort the quality of the picture. In portraits this can make it look more anonymous as their face cannot be clearly seen.
To liquify an image:
First go to filter, then liquify then select the icon along the edge of the screen relevant to which type of tool you want to use, then edit the brush size depending to how much of the picture you want to manipulate.
To Tilt Shift:
filter, blur gallery, tilt-shift, hold down command key and drag the grid to the place you wish to be focused. The shift grid can be rotated and adjusted.