You need to add the weapons in the config.lua and their respective images.
Add the weapon under WeaponNames category in config.lua. For instance:
Copy one of the above and then add your new weapon.
Add the resepctive image in the path "html\weapons" and make sure it is named to the same in config.lua. For example, WEAPON_VINTAGEPISTOL will have the name "vintagepistol.png"