I picked up a relatively cheap helmet last year (which I have since identified as a Polish wz-50 from the 1950s) and thought I'd customise it a bit, Full Metal Jacket-style, with a slogan on the front and a couple of logos to either side. It also gave me the excuse to try out for the first time the airbrush I'd bought at least a year ago.
On the front, the brush-painted lettering. On the right-hand side, I thought of the idea of tally marks, then decided to have them be in the shape of bullets just to make it a little more interesting. To the left, because I'm a fan of the Fett, the bantha skull (which actually looks nothing like a bantha skull and which some hardcore star wars nerds would argue over whether it's actually the skull of a mythosaur or of some guy called Jaing).
The helmet came with a new netting when I bought it, so I simply dirtied it in some mud to make it look a little older.