Easy Spritework: N2 Closet
Created by: Kurfursten
For years, the Vox outpost has had alternate O2 lockers that instead contain only N2 tanks and Vox breath masks. If you're a new contributor looking to cut your teeth on something easy, this is about as simple as it gets -- recolor an existing locker and change O2 to N2.
You can find O2 lockers under utility_closets.dm, look for /obj/structure/closet/emcloset/vox and simply set the icon states for open and closed to the names you've given the new sprites in closets.dmi (this is the same icon file where the O2 locker sprite is used).