Decals

#Use the wand to select the black areas and press delete twice. That will leave us something similar to the image to the right.

:*Make sure the layer you are working isn't locked. If it is, duplicate it to a new layer and delete the locked layer.

#Go to Layer > Transparency > and select 'Add Alpha Channel'

#Select the 'Fuzzy Select Tool'

#Set the threshold to '10'

#Select the black area and press delete twice

#In photoshop, go to Layer>Layer Style>Stroke. Change the stroke color to black and the size to '10'.  

#Select your main layer and create a duplicate layer by going to Layer> and choosing 'Duplicate Layer'

#Using your Fuzzy Tool, click in the transparent background area.

#Select the skull by inverting your selection. Go to Select> and choosing 'Inverse'

#Create the Stroke by going to Edit> and choosing 'Stoke Selection'

#Copy the settings from the image to the left

#You should still have the outline of the skull selected.

#If you do, simple press delete and you should get an image similar to the one to the left

:*If you accidentally deselected the skull, just use the fuzzy tool to select the skull in the other layer, invert the selection, and press delete.

#In photoshop, the easiest way for me to do this is to create a new transparent layer below my current one, then merge it down. Go to Layer>Merge Down. *Using Layer>Flatten Image will fill in my background with white which is something I don't want.

#Now I can use my magic want to easily select my image by clicking the empty area, then inverting my selection by going to Select>Inverse.

#In Gimp, simply go to Layer> and choose 'Merge Down' until you only have one layer left

#Create a new channel by clicking 'Create New Channel' at the bottom of that window. That gives me a black square with an outline of my crossbones.

#I want to fill that area with white so it will be visible in my decal. Go to Edit>Fill and use White.

#If you want to blend it to let some of the dirt and paneling of the mech show through, make a color that is 80% grey and fill the skull and crossbones with the paintbucket.

#After you fill it, you can deselect the image.

#In Gimp, right click on your layer and choose 'Add Layer Mask'. Choose 'Transfer Layer's Alpha Channel' and press 'Add'.

#If you want to blend it, select your skull (Fuzzy wand/Invert) and use the paintbucket with a color of 80% grey and fill the skull and crossbones with the color. You should see the grid behind it slightly show through.

#Once you are done, right click on the layer and choose 'Apply Layer Mask'.