Totally cosmetic things I think it'd be cool to see in a future release:
1. THIS DOOR IS LOCKED: Locked doors in a variety of levels have no message come up when pressed, which of course the original game had for (most) doors. Would be cool, for purely nostalgic purposes, for some doors to have that added back, like in Facility, for example.
2. SHOOT OUT THE LIGHTS: One of the only levels where you can run around shooting out the lights for fun/target practice/etc. is Bunker Classic. Many original GE levels had destructible lights, and Perfect Dark expanded upon that by changing the lighting in the area after they were shot out. Would be cool if some classic maps had destructible lights added back, and if some of the reimagined maps had destructible lights that change lighting effects (marginally) when shot out. It was always fun watching lights and such pop out in a random firefight... especially since they didn't magically "respawn" afterwards and stayed out, like a battle scar. Along a similar line, would be cool to shoot the door buttons on Silo like in the original game, too.
3. DESTRUCTIBLE OBJECTS: Crates were common in some of the original GE levels, especially classic Archives. Would be cool if more of the objects in reimagined levels (like Facility Backzone) blew up after 5 shots; especially when opponents are hiding behind/near them. Bunker has a lot of computers/etc. that blow up, but most levels don't (some shouldn't, of course, but some have wiggle room for additions I think). A lot of the reimagined levels have some scattered objects that just seem like they should explode when shot but don't... like fire extinguishers, barrels, crates, maybe even a table or chair!
4. DEPOT RARE LOGO: Cool Easter egg from the original game was the faded Rare logo towards the end of the level, on the wall where you shoot to lure the guard out of the final train... this spot in the GE:Source map is blank, would be a cool cosmetic tribute to the original to, for example, put the new GE:Source logo in that spot as an Easter egg nod.
5. FACILITY DOORS: I know there's issues with doors in the current engine; would be cool if they eventually get worked out so Facility Classic can get all of its doors back; Facility is the "Lost Temple" of GoldenEye (see: most popular competitive map in StarCraft), so even the smallest changes alter how the map is played and balanced compared to the original... having the doors back would close things up a little/give people being chased more opportunity to get away/just feel right. Same goes for the middle "quick opening" metal door - right now, the classic version *almost* has the timing right, but it's still a little slow; the reimagined version doesn't alter the timing of that door at all, I think.
6. SNIPER SLAPPER: When you have the sniper rifle in your inventory, would be awesome if your slapper was the sniper rifle butt like in the original game.
7. ALARM TIMER: In timed matches, would be cool to have an alarm go off during the last 10 seconds, like in the original game. If added, I think this feature should be toggleable as an option in case some players don't want it, maybe even with a customizable sound file for which alarm you want to play if you don't like the default one.
Again, all totally cosmetic, probably lowest-priority things, but it is my nostalgic wishlist!