We're going from to
Step 1: I added a new layer, moved it beneath the layer with the image and set it to 40% before filling it with the colour #FAF4B6. I also set the original image to Linear Light in order to lighten the image up a bit.
Step 2: Now I copied the image and set it to Multiply, keeping it at 100% as I thought it was a bit too bright.
Step 3:To get more visible edges I copied the image once again and used the filter "Find Edges" and inverted the result. Then I set the layer to Soft Light at 30%.
Step 4: To get a bit colour into the icon, I added a curves layer with the following numbers (in/out):
They are mostly the result of playing around as I'm still getting used to the idea of using adjustment layers (the same goes for the next two steps).
Step 5: Now I added a Brightness/Contrast layer to add more contrast, which I left at +14.
Step 6: The last adjustment layer I added was a Color Balance layer.
Step 7: The result of the last step inspired me to add a coloured background and I chose to go with green. So I added a new layer and filled it with a dark green (#164C08, Soft Light 100%). I also added a mask to keep the background only. In two more steps I added another layer filled with a light green (#C5FAB6, Hue 20%) beneath the dark green one and a yellow (#FEF487, Soft Light 30%) one above the dark green one before I was satisfied with the background colour.
-> -> ->
Step 8: Now I turned my attention to the person depicted. I added another layer and enlarged the entire icon until it was large enough for me to draw over the lips with red(should be #FA4B4B as this was the only layer where I forgot to note down the colour) after I was done, I set the layer to Color at 60%.
Step 9: As I thought it was still lacking something I decided to add some skin colour. Here I played around with various colours starting with peach before I finally settled on a brown (#8B6106), setting it to Soft Light at 60%, before declaring the icon finished.
At the end my layers looked like this:
This was my first tutorial so if I missed anything and you have questions, feel free to ask (I also hope that I found reliable sources for translating the tools I used).