I started with this cropped picture. (Original picture from InFEDs)
First thing I did was duplicate the layer (Layer 1). I desaturated this layer, applied Gausian Blur with the value set to 2,3. Then I set the layer to Overlay 100%.
Way too dark, so I added two Screen Layers in between the Background Layer and Layer 1 (see what looks good - sometimes you need more, sometimes less). I'm not sure, but I think I applied Smart Blur to either one or both of these layers. (Sometimes, if the contrast or the colours are too bright, you might want to lower the saturation of the screen layers, too.) This is what we've got now.
Now, the blueish colour did look good, but I wanted something a bit different. So I added this warm orange layer on top of everything.
And set it to Vivid Light 55%.
Next I added a simple 1px black border (Ctrl+D-->Edit-->Stroke), and that's it. Simple, but looks good, me thinks.