Result:
BEFORE > AFTER

1. First step is to get an image that you are going to lighten, i will using this one:
Image

2. Now open up photoshop and open your image that you want to lighten up. On the image layer selected go to Layer > New Adjustment Layer > Levels. And now a window will come up called 'New Layer' just leave everything to default and press ok. now setup the settings.
Image

3. Next go to Layer > New Adjustment Layer > Brightness/Contrast and have the settings as below:
Image

4. Now duplicate the ORIGINAL image you wanted to lighten, not the image we just edited, but the original one and change its blending options to 'Color'.

5. Next duplicate another layer of the ORIGINAL image and change its blending options to 'Lighten' and go to Filter > Distort > Diffuse Glow
and put in these settings:
Grainness: 5
Glow Amount: 5
Clear Amount: 10
Once your done, click ok.

6. Now go to Filter > Blur > Gaussian Blur and set the radius to 1.0

OPTIONAL STEP
If you do not wish to do this step, you can skip to step 8.

7. This step works in some images that already have a bit of light. Duplicate the ORIGINAL Image and change the blending options to Lighten and opacity to 50%. Now go to Filter > Sketch > Halftone Pattern and set the settings as:
Size: 1
Contrast: 10
Pattern Type: Dot

8. Now make a new layer and get the Paint Bucket Tool (G) and change your foreground color to white and paint your whole canvas white. Set this layers blending options to Soft Light and the opacity around 25-50% (whatever looks best).

9. And your done! If you have any problems check the layout of your layers, this is how it should be:
Image

This concludes our tutorial, you should have something similar to this:
Click here to view!

Examples of what you can make using this tutorial:
Example 1 Original > Example 1 Edited
Example 2 Original > Example 2 Edited