A little experiment tonight - I'm going to work up the skeleton of an adventure using the "random file" function at Wikimedia Commons. Now, you can't do anything with some of these random files, so I'm going to take every single one in turn, but I'll do my best with most of them to fit them into the scheme of the thing.
STEP ONE - LOCATION
Every good dungeon needs an entrance. My first image is actually a cheat - I'm using the picture of the day, the Temple of the God Wind in a Mayan ruin.
There's the entrance to our adventure site - a ruined temple. Even though "God Wind" sounds like it has something to do with divine flatulence, we'll assume we're talking about a wind deity. Let's work out some wandering monsters:
1. Wind Priests - half-naked blokes with censors of poisoned gas (sleep gas; they're immune) and light maces
2. Small Air Elemental
3. Fusillade of poisoned darts (save vs. paralysis)
4. Giant Constrictor (wandered into the place from the jungle)
5. Pirates (exploring the ruin; their ship is anchored off the coast)
6. Albino Apes (just because they have a place in any ruined temple)
STEP TWO - THE BIG BAD GUY
Since I'm thinking more in terms of a short adventure than a mega-dungeon, it's nice to have some monster or NPC sitting on top of the food chain. Not only is he/she/it the ultimate challenge of the place, knowing their identity in advance let's you weave their presence throughout the place.
My random file - Barack Obama. I'd love to expand on this, but I like to keep politics out of this site, so I'll try again. The next file is EZ Tondo - some sort of German store I suppose. The image doesn't help, but how about an exiled Teutonic Knight who dabbled in black magic and has now taken up residence in the bowels of this pagan temple, adopting the identity of Tondo, Son of the God Wind, and cowing the locals into serving him.
Tondo will be a 4th level fighter and 6th level anti-cleric (dual-classing, dontcha know), and always accompanied by four of the aforementioned wind priests (2 HD each).
STEP THREE - THE MACGUFFIN
Now we need a reason for the adventurers to delve in the place, beyond simple loot. I get "Cathagenian ruins in Tunisia", which brings Hannibal to mind, of course, and elephants, and thus a figurine of wondrous power, a pretty spiffy relic to delve for.
STEP FOUR - THE FIRST GREAT CHALLENGE
Just within the entrance, we need some wondrous challenge to whet the players' appetites. I randomly get an image of an altar in a church. Our first great challenge, then, is a trapped altar dedicated to the God Wind. Maybe it looks like a pipe organ. You have to play the proper tune to open the doors into the dungeon, with each mistake summoning a monster or bolt of lightning or gust of razor-wind - something like that. The notes are secreted within a bas-relief of a gaggle of sylphs with open mouths, as though singing or shrieking, the mouths being at different heights and thus corresponding to musical notes. No, the ancient Mayans did not use this sort of musical notation, but since the players probably are not ancient Mayans, the concept works for them.
STEP FIVE - GUARDIAN OF THE FIRST LEVEL
We need a good (or evil) guardian of the first level - a monster or trap who keeps people from getting to the lower level, where the MacGuffin and Big Bad Guy are hiding. I get this ...
Honestly, I have no idea. But it does give me some inspiration - I'm picturing a person grabbed by legs and arms and pulled in a most inconvenient way. But how?
Perhaps a well lined with hundreds of manacles embedded in the walls. The way to descend would be to either climb down a rope or climb down using the manacles as hand- and footholds. Naturally, the things are animated, and at some point attempt to clamp down on people's wrists and ankles (Reflex save to avoid). Maybe they then pull the person, or maybe they just hold them while some winged goblins fly up from the darkness and attack. Either way, it would make for an interesting and challenging combat.
STEP SIX - THE BIG MYSTERY
So, six images gives us the framework for a (hopefully) entertaining dungeon. We would now need to draw up the levels and sub-levels and stock the chambers with monsters, traps and treasure. Remember, random isn't just good in a game, it's also good for creating a game - random inspirations to set your little grey cells to firing and creating things even you could never have known were lurking in you campaign world.