One method I use to create abstract images is camera movement. You can create very different results depending on how you move the camera: up/down, left/right, or rotating the camera. Shutter speed also plays a role, since it controls how much time you have to move the camera. Generally the slower the shutter speed the more abstract an image you can make (for better or worse!). Experiment with theses variables to find a look you like, as well as what works best for a particular subject. Another option to play with is single exposure vs. multiple exposure. Some cameras (most Nikons, and now some Canons) offer an in-camera multiple exposure function. This feature automatically blends together a series of images, and is one of my go-to methods for creating impressionistic images. This Monet-esque scene of water lilies and lily pads is an example of a multiple exposure. For multiple exposures I shoot between six and ten images, moving the camera a very small amount between shots. The small amount of movement is enough to obscure the fine details, yet still retain the rough shape of the elements in the image. When doing any camera movement technique take the same shot a number of times because no two images will be the time (I usually do at least five). This will also help you get into the rhythm of the camera movement.