Hey
Lookin good mate, but I just realised everyone's using thick pixel borders! >_< You can do this :
1) Make a new layer
2) Go to Edit
3) Hit Stroke
4) Select around 2px and set the colour to white [press ok]
5) Set the layer mode to Soft Light
6) Go to Layer Styles and add a 1px black stroke, to give you an inverted border thingy
Hope that helped (apparently it's much more professional) give it a try m8, see if you like the outcome.
Also you can if you want add a bit more depth to the skull, hit CNTRL + J two times to make three layers of the same skull:
1) Set the first layer to Normal [lowest layer/original]
2) Set the second layer to Hard Light [middle one]
3) Set the third layer to Soft Light [toppest one]
4) Go to Image -> Adjustments -> Threshold
5) Fiddle with the slider so that there is relatively little white (usually towards ---> that end)
6) Then go filter -> blur -> guassian blur, and set it to a low around 2.0 or less
7) Delete around the edges and work some art to give the features a buff up
Hope that helped! O_O