I think this thread is a good idea. But it's often easier to check for existing pictures and use them instead of creating your own. Here's a short list with file names and descriptions of all spotlight pictures from AoM, AoM:TT, 'The Golden Gift' and EB's bonus scenario 'Close to Home':
spotlight_01 - Arkantos' Attributes
spotlight_02 - Villagers, Farms and Granary
spotlight_03 - Villagers building
spotlight_04 - Arkantos fighting a Cyclops
spotlight_05 - Hypaspists
spotlight_06 - Toxotes
spotlight_07 - Fishing Boats
spotlight_08 - Donkey Caravans
spotlight_09 - Prodromoses, Hippikons
spotlight_10 - Centaurs
spotlight_11 - Petroboli, Helepoli
spotlight_12 - Cyclops and Chimera
spotlight_13 - Shades
spotlight_14 - Labourers building a Monument
spotlight_15 - Pharaoh empowering a Gold Mine
spotlight_16 - Slingers, Chariot Archers
spotlight_17 - Sphinx, Scorpion Man and Petsuchos
spotlight_18 - Naval Battle
spotlight_19 - Pharaoh with Relic
spotlight_20 - Axemen, Spearmen
spotlight_21 - Mummy and Phoenix
spotlight_22 - Colossi
spotlight_23 - Camelry and War Elephants
spotlight_24 - Cows, Deer and Pigs
spotlight_25 - Hersirs and Ulfsarks vs. Battle Boar
spotlight_26 - Dwarves, Ox Cart and Gold Mine
spotlight_27 - Mountain-, Frost- and Fire Giant
spotlight_28 - Jarls and Raiding Cavalry
spotlight_29 - Valkyrie and Ulfsarks
spotlight_30 - Ballista and Portable Ram
spotlight_31 - Ulfsarks
spotlight_32 - Huskarls and Throwing Axemen
spotlight_33 - Troll and Battle Boar
spotlight_34 - Naval Battle
spotlight_35 - Loki's Ship
Spotlight_x01 - Atlantean Citizens
spotlight_x02 - Sky Passage
Spotlight_x03 - Oracle, Shrines and Relic
Spotlight_x04 - Soldiers and timeshifting Building
Spotlight_x05 - Atlanteans fighting Egyptians
Spotlight_x06 - Odysseus, Hippolyta and Polyphemus
Spotlight_x07 - Atlantean Titan
Spotlight_x08 - Soldiers and Monsters in a Vortex
Spotlight_x09 - Traitors God Power used on Fanatics
Spotlight_x10 - Animals on lush near a Temple
Spotlight_x11 - Automatons rebuilding each other
Spotlight_x12 - Implode Sphere
spotlightmc_01 - Ragnarok Heroes vs. Mountain Giant
spotlightmc_02 - Longboats
spotlightmc_03.tga - Plenty Vault
spotlightmc_04.tga - Gatherers and Walking Woods
spotlight_eb - Fire Giant and Throwing Axemen
So far I've always been able to find something which more or less matched my needs.