This is a turret from the game Portal, which I have never played, although we have both the desktop toy and the plush toy because we think they are cool.
I haven’t really played with the effects in GIMP that much. The background is a Gradiant in a clockwise spiral. It had colors in it but after I used the Filter of Emboss, it removed the color and gave it that wild feel–not quite as 3-D as I’d like but a cool background.
A Daily Doodle 