I've found Pony is way more picky at backgrounds than SD1.5 was (you could throw really random locations at it and they'd blend together into something interesting), and even some stuff it recognizes doesn’t always get generated well. Here I’m listing tags I’ve discovered make good (or at least not blatantly non-Euclidean) backgrounds on their own (without additional LoRA). This is mainly to keep track of it for my own purposes (read: I edit this without change-log when I find something neat. I try to keep new stuff at bottom), but sharing this means other people can share their discoveries in the comments. (Backgrounds are an option for one of those big prompt comparison chart articles for anyone with the will and resources to try .) Some or all of this may work with Illustrious (ILXL), but I haven't tested any of it.
Update Jan 7: I have played around with Illustrious enough that I'm confident saying the majority of these should work there as well.
Tags after a comma mean they’re supporting tags that make it more fleshed out and I haven’t really tried using them without the first listed. A ? means I've had a good result with it but haven’t experimented with it (or the string in parenthesis) enough to say for sure it’s useful or if it’s just other prompts/the LoRAs that in the mix doing the lifting/getting lucky.
Outdoors:
(badlands, crater, cliff, mountain?)
beach, sand, ocean,
canyon
castle background
city, cityscape, street, on roof,
desert, sand (, mojave desert?)
fantasy village background
farm
field
forest, trees
laboratory?
mountain
onsen, steam, wet, water
park
(ruined city, toppled skyscraper, rubble?)
slums, building, outdoors, garbage, rubble, ruins
wasteland, grey ground, rock, bare tree
plains, grass
alleyway, brick wall, trash can, dumpster, graffiti,
garden, flowers (potted plant as negative if you want everything neatly in planters)
mountain pass, (ridge?) Generates pic in mountains, though not as high up as desired.
coast (combines well)
ancient ruins, white marble pillar
airplane interior (window, sitting)
fitting room (much more stable on Illustrious than Pony. May want curtain, door, doorknob on negatives)
mall (this is more of a Japanese style multi-level indoor shopping complex than the open plaza American mall. May be SD's tendency to make backgrounds hallway like unless told otherwise)
Indoors:
bunker interior, underground bunker,
castle background, throne,
catwalk (\modeling\), stage lighting, crowd
classroom, desk, blackboard
colosseum background (this one, oddly, only seems to work better with Pony than Illustrious)
fantasy village background
(fantasy ruins background, maze, labyrinth?)
hallway
living room, couch
shower (\location\)
spacecraft interior*, (spacecraft bridge?)
arcade, arcade machines,
store (adding adjective for store type?)
casino
club (needs "strip club, pole" in negatives)
bar, bar (place), saloon background, (the first two combine to make the bar's bar appear)
shouji, fusuma, tatami (Do not use "Japanese architecture". May need negatives like doorknob, outdoors, open door, window)
middle eastern architecture, palace, cushion,
locker room, locker, tile floor, bench,
garage (you will need to tag motor vehicle as negative if you don't want a car)
underground, cave (negative sun, sky, window, outdoors to avoid sunlight shining in)
warehouse, crates (this one is a bit checkpoint dependent)
Supporting objects:
building
carpet
ceiling light (great if you want ceiling to appear due to depth or angle)
grass
overgrowth, vines,
scenery, landscape
sidewalk
tree
trees
waterfall
path
wall/floor (ceiling works, though I've found ceiling light to make more natural in settings where it fits)
river
mountain (This makes a mountain in the background, rather than set your image on a mountain)
wheat (the first crop I've found that's consistently generated and generates as a crop instead of prepared dish)
treasure hoard, coins
lava
crowd (use with “solo focus” recomended. ILXL handles this better than PDXL. Try playing with weight to get the scene more or less densely packed. "females only" may reduce presence of males in crowd)
shipping container
trash
graffiti
sky, cloud (often come by default, but can help angle outdoor shots away from the ground. You can color these, e.g., "black clouds", "red sky")
rice paddy (only this specific name works well)
Genres:
These have an influence on background. Beware their influence on other parts of image.
science fiction
cowboy western
fantasy
Enhancers:
aerial photography (if you ever feel the ground is too close. Useful for flying etc.)
cramped
night,
underground
dark
(black background:0.5) (Makes things darker. At full strength this tends to put a lot of "blank" space in the background. I've got some notes on a full article for this and other [color] backgrounds] but haven't had time to experiment when the generator wasn't messing with colors)
Negatives:
sun, sky, window, outdoors (helps makes indoor settings truly indoors)
Interactions:
sitting
laying
leaning
against wall, (leaning)
the conjunction "on" seems to produce good results when paired with background objects. "sitting on chair", "laying on bed", "leaning on rail" etc.
Known to models but poor results:
“Athletics Field” and/or “Track and Field”
Basketball Court
Bedroom (This is one of the worst offenders. Especially if doors or windows are present. Some checkpoints tolerate it better than others and Illustrious is better than Pony, but it’s rarely great. I've found it is pretty good at checking for overbaking in epoch pics though.) Update: Adding "wall" helps stabilize this one for some reason. Still not ideal, but vastly more usable.
Japanese architecture (this one needs heavy supporting word use to make clear which era/kind of Japanese architecture you mean, and I've concluded that you're better off just calling the elements you want)
*This one will alter the overall theme of the background a good deal.
(The cover image is "score_8, score_8_up, score_7_up, source_anime, anime screenshot, no humans, scenery, landscape, canyon, waterfall, outdoors" in WAI-ANI-NSFW-PONYXL
Update Dec 19: Realized I hadn't updated this in a while, so added a bunch of new tags I have found.
Update Feb 2 2025: Added some more stuff, including new sections on enhancers and interactions.