Quake is the DOOM type game put on the market immediately after DUKE in 1996, and is the succeeding game of DOOM which ID software made. It is the feature that the game is a perfect 3D game by which the character and the item were all made from the polygon. It seems that arms and the characters are acting as the inheritor of DOOM.
The hero of QUAKE1 attacks into the different dimension in order to repulse the monster invading from the slip gate (different dimension tunnel) which appeared in DOOM. The atmosphere of a different dimension seems to be a medieval castle, and is quite dark. Enemies are the armored knight and zombie, and the big savage beast which jumps about.
The upper picture is the hero of QUAKE1 as you know. He is a 'slip gate investigator', and is not a combatant. Although he came to investigate a different dimension tunnel, he was involved in fighting. Probably he seems to be very unpleasant at such a reason.  His posture is the posture of the scene where the big monster was defeated in the end of the game.
RANGER appears also in QUEKE3 and is protecting the front gate of the arena. The dress in QUAKE3 has a bright color. :-)
QUAKE2 is war in Planet STROGGOS. Enemies are extraterrestrials with the body of a machine. The atmosphere returns to hard and powerful touch like DOOM. (The strongest arm of DOOM BFG also appears.)  However, women appear in QUAKE2. You can choose a man or a woman as the player in match play, and fearful women like Iron Maiden appear.
'3' is a game only for match play, and you can choose the character of DOOM or QUAKE. You can also fight with a computer by 'BOT match mode', and can play with stand-alone PC. The computer is very strong!
Lower pictures are the characters of QUAKE. They are all individual.
The instructor woman who fights on the first stage when you choose BOT match in QUAKE3.  If you shoot a shotgun, she will fall exaggeratedly. According to the description, she was the instructor of DOOM army, before coming to the world of QUAKE3. Then, she is being covered with the helmet of DOOM army. 

The double shotgun of a heart type fits her well.

He is an enemy's cyborg fighter, and is somewhat stronger than an ordinary soldier. He does not have a gun, so his main arm is right spear. When he discovered you, he runs crying somewhat, and knocks with the right hand. The attack is very effective. He is the rush fighter who does not know retreat!

The meaning of his shout 'Te-shi-missa(?)' is not understood. The shout of Iron Maiden 'Choi-Pa(?)' is also uncanny.

A strange living thing only with the body, and an eyeball and hands. But he is so strong at match play that I am surprised. It was troubled. An antenna is somewhat pretty...
She is the fearful woman, who has a rocket launcher and the body of machine. In fact, although she was a very fearful figure, I drew her prettily.