Preview:

Warning! contamination ahead. suite up and get ready for an awesome effect tutorial :)

Getting started.

In this GIMP tutorial i used two elements. the nuclear sign and the watercolor background so go ahead and download them from the following links.

Nuclear sign: i can't remember where i got this freebie icon so I've placed it on our sever for download
Water color texture can be downloaded from Go Media's free Watercolor Pack sampler, download

Step 1

Create a 600x450 image. if your going to use it as a wallpaper i suggest you create something bigger.

Step 2

Fill the background with black and place our nuke sign in the center of the canvas.

Step 3

Now right click on the nuke icon layer and click on Alpha to Selection, then go to Filters>Light and shadows>Drop shadows, set the settings to Offset X:0, Offset Y:0, Blur radius:380, color a5ef17, Opacity 100 , and un-tick "Allow resizing".

De-select selection by going to Select>None . this is how it should look

Step 4

Now Repeat step 3 but this time set the blur radius to 100.

Step 5

Next open mdp-watercolour60.jpg from the zip file you downloaded off go media and open it in gimp, then resize it to 700x990 by going to Image>Scale image.

Step 6

Next change the image to black&white by going to colors>Desaturate. then go to colors> Brightness and contrast
and set Brightness to -80 and contrast to 118.

Step 7

Now insert the watercolor image above all the other layers and then rotate the image on an angle of 128 and set the layer mode to Overlay.

Step 8

next turn off the textured watercolor layer by clicking on the eye icon in the layer dialog this is so it doesn't get in our way.

Step 9

Next grab the Path tool and create a curved path. the idea is to start all paths from the edge of the icon, as if its coming from behind it.

Step 10

Create a new layer. change your foreground color to yellow fdf23c and with the path still active go to Edit>Stroke path and set the value to 3px.
note* if your path disappears go to the paths dialog and right click>path tool.

this is how it should look

Step 11

Select the easer tool, ease part of the overlapping line so that it looks like its coming from behind the icon. then use the Circle fuzzy (19) easer brush to get a faded effect for the end points.

Step 12

Next will add a glow to our stroke by going to the path dialog then "right click to > Path tool" on the path we previously drew.
then select Circle Fuzzy (17) from the brushes dialog and go to Edit>Stroke Path and select "Stroke with paint tool.
finally set the layer to overlay.

Step 13

As we did in step 11 use the Eraser tool to clean up the stroke ends.

Step 14

Create three more strokes each on there own layer with each layer's opacity set to 39.

Step 15

Using the same technique as the glow strokes in step 12, will create some particle effects on two of the paths.

Create a new layer, Go to the path dialog then "right click> Path tool" on the path we previously created.
then select Sparks from the brushes tab and go to Edit>Stroke Path and select "Stroke with paint tool. repeat this to the top left stroke and when your done set layer mode to Overlay.

Step 15

We could stop here but i think this adds a nice touch to it :) with the "spark brush" randomly apply some here and there, not so much though.

Step 16

Re-activate the watercolor texture layer by clicking on he eye icon and set its Opacity to 85. and thats it :)

the gimp XCF source file is attached below as always. enjoy!