Having an issue with this bike override not displaying the correct icons for all presets.
To make it I cloned the EA bike with S3OC without renumbering, opened the package with TextureTweaker3, clicked "upgrade to 4 channel CASTable", stripped it to just the first preset, then duplicated that preset to create my new ones.
Any ideas on how I can get it to update the thumbnails? .package is attached if anyone would like to poke at it with a stick.

Here I've gone through and selected each preset and you can see the icons for three of them do not match the updated materials/overlays I've assigned and instead retain the old EA defaults. Ignore the RGBY colouring, I haven't picked pretty textures yet.

EA included the thumbnails for most of the base game objects in the install directory, so to fix those thumbs you'll either need to make overrides for the incorrect pngs or change the number in the Materials "Unknown3" field in the OBJD for each of your new presets to something different than what EA set it to. The second option will trigger the game to generate new thumbnails in the ObjectThumbnails package in the user files (like store content does), but I'd actually recommend the first technique since it's what EA did and seems to be more thorough/reliable to me.

When I make default replacements for my game, I create overrides for the 54x54 png and the 128x128 png sizes. The smallest size doesn't seem to appear in the game anywhere in my testing, but I could definitely be mistaken about that. Anyway, what I'd do for that package is once you've generated your pngs (whether Maxis match ones or created custom ones in photoshop or wherever) go to the largest thumb (type number ending in B6), right click and duplicate it for however many presets you created. Then for each one of those new duplicate thumbnails change the last digit of the group number to match the corresponding preset number in the Unknown3 field in the OBJD. So for that bike, you'd end up with eight 128x128 thumbnails, each one with a different group number 1 through 8. Repeat that for the 54x54 size png (type number ending in B5). Then go through and replace the pngs with the correct images (right click -> replace in S3PE). Finally, do one more duplicate for both thumb sizes of the FIRST preset's thumbnail and change the group number to end in 0. (That one is used in a couple of places in buy mode, although I can't remember exactly where at the moment.)

I can do it for you if you'd like, although it's really quite easy once you do it a couple of times. Or if you don't want to bother, just fiddle with the number in the Unknown3 in the OBJD for each preset until it clears out to a new thumbnail. I hope that makes sense! And you know where to find me if you have problems or questions.

Oh I could hug you right now I fiddled with the Unknown3 numbers (since I'm lay-zee) and they're all showing correctly now. Just curious, how would you source the images to use as replacement thumbnails? Would you save a preset with CASt then track down that thumbnail file in the game files to extract it? Where are the preset thumbs even stored?
Thanks a bunch! <3

If you want Maxis match thumbnails, then yes that's exactly how I would do it. Fiddling with the color of one channel even just a teeny tiny bit gets the game to recognize it as a new preset so you can save it, which then generates a thumbnail in the ObjectsThumbnails package (in Electronic Arts/The Sims 3/Thumbnails folder). You can locate the exact pngs you want within the package by sorting the resources by type and then by instance number. The new thumbnail you generated will have an instance number that matches the instance number of the object's OBJD, and then just export it to file and right click -> replace to make it an override (as explained above).

If you don't want a Maxis match thumbnail, then it's just a matter of taking a picture of the object (or finding/creating an icon of it somehow), resizing it to 128x128 and later 54x54, and saving it as a png.

So glad you got it working! I'm really looking forward to downloading the final version. <3 Just out of curiosity, are you planning to create something similar for the children's bicycle or no? I would LOVE it if you were. But no worries if not, lol. It's just such a cool idea.

Yeah I'll be doing the children's one too, I think they use the exact same textures so I can just import them without having to change anything.

Thanks for your help lady cake!