Example 1: When we remove some of the sharpness of an image, we remove some of the reality. We can remove sharpness by adding noise or grain, or by blurring the image. One of my favorite techniques for adding grain is to use the Diffuse Glow filter in Photoshop.
Increasing contrast also can reduce details in an image. After increasing the contrast (Image > Adjustment > Brightness/Contrast) in my image, I applied the Diffuse Glow filter.
This is my original shot. It's not bad, but the image with some of the reality removed looks much more artistic.
Example 2: Here's an image I call "Green Eyed Lady." It's a dummy album cover I created just for fun. The process, which creates a very high-key image, is easy to do.
The first step is to duplicate your file and then to desaturate the top layer (Image > Adjustment > Desaturate).
Next, adjust the Levels so the picture has few midtones. Start with the Highlight slider (the tiny triangle on the right). Basically, you want a black-and-white image. Note the difference in the position of the sliders in the "before" and "after" shots. I moved the Highlight and Grayscale slider (middle slider) to the left and the Shadow slider to the right.