try taking a copy of a layer and use the smudge tool with your stylus to push the pixels around like digital paint. Experiment with the "strength" setting and the layer opacity.

another thing to do is to use the clone tool on a blank layer (of course you need to select the target from a layer with pixels on them... but switch to your blank layer to "clone to"). this way you can use the layer color mode too to can a desired effect...

i'll try to make a quick example

retrocity