The jetpack is, of course, the iconic prop for any sci fi setting, but when I was a kid, the thing that fascinated me the most about Star Wars and the like was always the cool helmets everyone got to wear.
Put it this way: If I'd been Harrison Ford, I'd have insisted that they add a cool helmet to my wardrobe. Sacrilege? Maybe, but it was sincere sacrilege at least...
Since I don't have the facilities to do vacu-forming (yet) all of my helmets so far have been modifications (sometimes pretty serious ones) and repaints of existing helmets.
NOTE: if you decided to do this, don't expect them to protect your head when you're done. The goal is to achieve a fun, cool-looking prop, not a piece of genuine safety equipment, even if you started out with one.
I decided early-on that in order to really sell the idea of a steampunk "Buck Rogers", I needed a helmet.
As is so often the case, I returned to the iconic "Spaceman Spiff" helmet sometimes worn by Calvin in the comic strips. I think Bill Watterson was working from the same childhood aesthetic as I when he created that (as well as most of the props for Calvin's imaginary exploits).
For my helmet, I hunted high and low for one with the right lines and ended up choosing a child's snowboard helmet that I picked up at a thrift store for a couple of bucks. I chose it for its art deco profile and resemblance to the "Spaceman Spiff" style helmets in my imagination.
The vented sides are one of my favorite elements. Combined with the aerodynamic lines, it really sells the space-opera effect I was going for. The knurled brass knob seen below is a bit of added bling that I picked up at the hardware store. It secures the lining and chin strap into the helmet.
I'm a huge fan of subtle design elements.
I've handled a number of reproduction and real helmets both real and decorative and even once got my hands on a Victorian-era brass fire helmet. All of the ones I liked most had embossed patterns worked into them, usually in an Italianate viniform motif. The Victorians loved this kind of decoration, and almost everything was decorated. In metalwork, however, they tended toward playing with light and shadow rather than gilding and paint like the suit of armor at the end of that second link.
To accomplish this effect, I painted swirling designs in thick acrylic paint between the first and second coat of metallic copper spraypaint. Then when I went over the whole helmet with washes of FW Burnt Umber acrylic drawing ink that I then ragged off, the ink remained in recessed areas and the raised areas remained bright, giving the illusion of greater depth than is actually here.
After the inkwash dried, I worked several thin washes of forest green into the creases to accentuate them even more and imply the sort of verdigris that builds up over time on real copper. This also had the effect of dulling the fake metal-flake effect given by the spray paints even further until the whole thing was virtually indistiguishable from the real copper wastebasket in my bathroom.
With all of the styrofoam yanked out, it fit my head much more closely than a ski helmet, which is one of the reasons it doesn't scan immediately as a repainted plastic ski helmet. I sewed-up a quilted cap liner out of linen to replace it. Naturally, this invalidates it as a crash helmet, but it fits more like a classic helmet this way and since it's only for costume use, I figured what the heck, why not? And Styrofoam's not very Buck Rogers anyway...