A few sections under "Imperium" (not an exhaustive list; I'm not a very serious fan):
Imperial Guard
Imperial Navy
Space Marines a.k.a. Adeptus Astartes
Adeptus Mechanicus
A picture marked Dreadnought (or the alternate spelling Dreadnaught), or Terminator, is probably a Space Marine in super-heavy armor. An Apothecary is a Space Marine, too. I saw reference to a Rhino, which is an APC the Marines use and the Guard don't (the Astartes are elite; the Guard are treated more as cannon fodder).
Any image for which the title includes the word "Titan" is likely to be a humongous mecha of the Adeptus Mechanicus.
Imperial Guard
Imperial Navy
Space Marines a.k.a. Adeptus Astartes
Adeptus Mechanicus
A picture marked Dreadnought (or the alternate spelling Dreadnaught), or Terminator, is probably a Space Marine in super-heavy armor. An Apothecary is a Space Marine, too. I saw reference to a Rhino, which is an APC the Marines use and the Guard don't (the Astartes are elite; the Guard are treated more as cannon fodder).
Any image for which the title includes the word "Titan" is likely to be a humongous mecha of the Adeptus Mechanicus.
-----
"The Lady of the Lake, her arm clad in the purest shimmering samite, held aloft Excalibur from the bosom of the water, signifying by divine providence that this was some killer weed."
"The Lady of the Lake, her arm clad in the purest shimmering samite, held aloft Excalibur from the bosom of the water, signifying by divine providence that this was some killer weed."