There's a console command server hosts can use to turn the gibs into things like gears, a burger, a spring, etc, but they don't usually use it, if someone is killed via a rocket launcher, the Engineer's sentry missiles, or bombs, the victim's character becomes small bloody gibs, they roll around for a sec and some blood decals appear where they go, when a player is shot, they have blood on their character, if they're killed, they just become a lifeless corpse and spectate other players until they respawn and their corpse is gone soon after