Firstly, I need items suggestion for Sad Satan (linked under my HA, be warned for moving images in their profile), his treasure is themed after Apocalypse + Frozen/Freezing (although I need more help with the apocalyptic side, didn't really look into the other part yet) I think sadness could be a theme too.
Also, how do you organize your TCs? I always get lost in that stage and end up trying to space out items that look alike 🤦🏻♂️
I normally group by item time. If there's multiple items in a set, I'll put them together, If there's no matching characteristics, I don't care.
I tend to group mine by story beats or certain plot significance. If they’re in the same kind of subgroup, I’ll try to organize them to be a pretty gradient colorwise. For example, all the toys in Jillion’s TC are either grouped by color or theme and then there’s a toy box near the end because that’s where all the toys go after playtime is over. Or I’ll organized based on certain ideas, such as Meili having a row with the fisherman doll + dragon to represent how dragons are synonymous with masculine energies and there’s the noblewoman doll + Phoenix due to how phoenixes are related to feminine energies in Chinese culture.
If you want to look at frozen/cold themes, Samsara might be good inspo.
omitted, brutalism and sprout might help with the tc? o: they have themes of kinda similar stuff, terrible events happening that lead to people abandoning places
sorting depends on the pet and what's in the tc tbh sometimes the items are similar enough that they look good enough as i throw them in like for brutalism above, sometimes it's by color which i do the most, some pets have it sorted to hint how the story progresses like hijiki's tc with normal food and then at the bottom it's poison and body parts cause oops that's not a normal food he's selling, similar with apiarist. or dead flowers at the bottom of missing's tc i hope i make sense lol. i dont know

Gonna edit this with some item suggestions soon!
I usually sort by colour and shade if I'm planning on a huge TC Andreu, or try to plan around theme + specific colours so that they'll look nice as a whole Laurentin. I've got one (fan) pet whose TC is sectioned chronologically, with items used to separate each section Foolish. Honestly my systems are kind of all over the place tbh, it's just whatever suits my wants at that specific time :'D
All of my TCs are a bit of a mess right now, but the idea is still there. For me, it's really dependent on character. I seem to usually group items based on "type" and then order them based on significance, within that the group is kind of random.
I did a lot of specific things for Thief's TC, especially since it's massive. A lot of things were grouped based on real world value. So the gems were ordered diamond, ruby, emerald, sapphire, etc. Coins were gold, then silver, bronze, etc. Anything with an aura/magical look was valued higher than a non magical ones and were ordered first with the idea that magical items would hold more value. He personally values books and knowledge really highly, so books are ordered pretty highly in the TC, above items that might be worth more in raw value. So ultimately it's just a mix of character and value for him.
Draco is ordered by items that represent significant story beats for him, then books, then potions, then ingredients. Within that, I grouped potions based on their items or sets and then ordered them in ROYGBIV since there wasn't much significance to how the potions were grouped like there was with Thief.
I don't really remember why 111 was set up the way she is, but I group items specifically on type for her. The beginning of her TC starts out with representing companions and from their all the guns are grouped together, all the armors, all the food, etc. On that note, 111 is my Fallout pet, so she's got some apocalypse stuff in there!