Okay so here's what I've found:
- Wood is the Bikini Bottom level texture.
- Purple is the Beach level texture.
- Castle is the Jellyfish Fields level texture.
- Jade is the Kelp Forest level texture.
- Spooky is the Phosphor Caves level texture.
- Using houses with a "2" next to it makes the house red.
- Using houses with a "3" next to it makes the house yellow.
- 1 is the default house texture (no need to place a 1 to even get it) and 4 makes the houses glitchy.
- Bird fountains are the Krusty Krab.
- Big pyramids are the Krusty Krab sign.
- Little pyramids are tall seaweed things.
- The orange circle next to the pillar is the flame object, but it looks a little different in KQ.
- Pillars are Spongebob's house.
- Green trees are Patrick's rock-house.
- The small traffic cone-looking thing are rocks.
- The wider traffic cones are sign objects. (these are just models, you still need to place an actual floor sign)
- White trees are the bamboo stick things.
- Small mushrooms is the umbrella.
- The object to the right of custom house 4 (I think it's a lamp in RTW, can't remember) are the little flowers.
- And the two objects to the right of the small pyramid are the horizontal and vertical road barricades.
Garden, Aztec, Cave, and Sand level textures will not work unless you copy them into the extracted "Graphics" folder from RTW's extracted "graphics" folder, however when I tried this a few more files were required to be copied to load the level such as the "gentele" files. Anyway, when copying these textures over you should not get a "This file already exists!" notification from Windows. If you do get it, then you're copying something extra that isn't needed.. I could be wrong though.
Also, I tried using the platinum editor just for trying out custom level textures by renaming "LV6" to "lv5", and it does not work (probably because of the LV6 file structure. Hex editing custom textures and backgrounds might work, but I have no idea how to do that). Custom Models and Houses do not seem work. I could be wrong though since it's been awhile since I've used the RTW editor. I'll let you guys check it out.
The music tracks you can choose in the editor have no effect in-game, probably because KQ uses a different kind of music format than what the other games do. (KQ uses Ogg instead of tracker music) Hex editing might work for changing the music, but I don't know what byte to change or anything.
As for the built-in backgrounds in the editor, you can use them if you copy them from RTW's graphics folder into KQ's Graphics folder.
Keep in mind that KQ's only background, Sky, uses the "cloud" image in the Graphics folder as well so be sure to change it if you're overwriting the game's original background.
If you need help finding out what to copy, KQ gives a "couldn't load" error with the filename of the graphic texture it couldn't load.
Incompatible objects not on the list:
- The switching conveyors.
- Lava Tiles.
- Lava Break Tiles.
- Electric Tiles.
- Ice Curve Tiles.
- Timer Buttons.
- Factories.
- The lightning effect.
Objects that look weird:
- Teleporters.
- Conveyor type 2.