I belive I started the "half sleeves" tradition in Chama back in 1981 or so. Some friends of mine who worked for the Sierra RR had them and I though they looked way too cool. My mom made mine back then, although Carmen makes a better pair now (sorry mom). As related above, they do wonders to save your arms from assorted steam engine schmutz as well as burning holes in your arms with mis-directed cinders. They also provide another layer of insulation when you are firing.
We provided JC Penney Big Mac hickory striped shirts to the guys. They are cool in summer, warm when its cool out, last forever, and look good with a pair of blue bibs.
We used to to a mass-order to Penny's in the spring for bibs (everybody bought thier own). Some guys preferred another brand. Big Smith was a popular alternative. I personally preferred Big Macs (Penny's) because they had real heavy duty clasps and the straps didn't slip out of adjustment.
Generally everyone wears their bibs over a pair of jeans. It gives more insulation from the fire when you are on the deck shoveling (your left leg will get fried otherwise). Also at the end of the day, you can skin them off and not leave 2 pounds of coal dust inside your wife's car.
I sould mention once I moved to the heat of Texas, jeans under one's bibs is a not too great idea.
Hats were up to personal taste. Most guys preferred blue traditional engineer's hats because they don't show dirt like striped ones. Good ones are hard to find anymore. I hate the "one size fits all" kind with the plastic strap in back. My mom made me a few real nice ones about 10 years ago using an old nasty one I had for a pattern.
Then there are the Derby Hat Guys.... This was started back in the early 70's by Jim Shawcroft when he worked here (Jim liked "distictive headwear"). He talked Russ Fischer and I into the idea. We bought cheapies at Woolworths in Durango (who'd wear a good hat on a steam engine?). Russ didn't wear his as much as I did and that started yet another tradition.
Then Stebbins stole my fashion statement.
