I crop the picture in an interesting (hopefully) way.
100px by 100px with 72 resolution pixels / inch
I duplicate the layer, and set the layer mode to screen.
I duplicate again, and set this one to soft light.
Now I go back to the original layer(background) and go to filter / sharpen / Sharpen
Depending on the cap, I can Sharpen twice.
Now I go to either the Screen layer, or the soft light layer and brighten one or sometimes both.
By going to Image / Adjustments/ Brightness and Contrast
I usually look at color now. You can change the picture alot by making the colors are crisp.
I try to change each layer a little with Image / adjustments/ Color Balance
By giving the picture more Cyan, and more Yellow (as an example) gave this picture less red, and more depth.
Messing with the colors on each layer, really makes a difference.
Now I like to combine what I've done.
Create a new blank layer on top of all of your layers.
Now press all these keys at once: CTL + ALT + Shift + E
Set this new layer to soft light.
This new layer is a combination of the other three layers. it makes a huge impact.
Everything after this is personal choices. You can give the icon more contrast
By adding adjustment layers/ (Layer / New Adjustment Layer / Levels or Brightness and contrast
This adds the brightness and such to your whole icon, instead of one layer.
then you can either copy the whole icon again, or go to Layer / Flatten image
this gives you one layer to blur out Sharpening noise, burn or dodge the light and dark areas.
Screenshot of layers
I hope this Helps.