Fogger: BETAZOOER Reptile Humidifiers... https://www.amazon.com/dp/B07YYYMRSV?ref=ppx_pop_mob_ap_share
Clay pebbles: Mother Earth Products HGC714114... https://www.amazon.com/dp/B01KYYZDUS?ref=ppx_pop_mob_ap_share
Activated charcoal: Hoffman 17502 Charcoal Soil... https://www.amazon.com/dp/B001ACPZ0W?ref=ppx_pop_mob_ap_share
Waterfall pump: PULACO 10W 160GPH Submersible... https://www.amazon.com/dp/B07YLHVZ4Q?ref=ppx_pop_mob_ap_share
Slate stone: Natural Slate Stone 3 to 5 inch... https://www.amazon.com/dp/B078B697CD?ref=ppx_pop_mob_ap_share
Live moss: Tin Roof Treasure Live Terrarium... https://www.amazon.com/dp/B0714FVV29?ref=ppx_pop_mob_ap_share
Grommet for hole for the wires at the top: HJ Garden 2pcs 1-1/2 inch Desk... https://www.amazon.com/dp/B07G83N99D?ref=ppx_pop_mob_ap_share
Cork backing (used to hide “shaft” where I ran cables and waterfall water tube): PINVNBY Cork Terrarium... https://www.amazon.com/dp/B08D6FKFFX?ref=ppx_pop_mob_ap_share
Sphagnum moss: Galápagos (05213) Terrarium... https://www.amazon.com/dp/B00KZDT346?ref=ppx_pop_mob_ap_share
Coco/Perlite soil mix: Uncle Bud's Coco and Perlite... https://www.amazon.com/dp/B091BKCNKM?ref=ppx_pop_mob_ap_share
I used expanding pond foam for the background. Most tutorials I saw said they used the brand Great Stuff, but I couldn’t find that. I just used whatever version of that I found at Lowe’s (home improvement store, not sure if you’re in the US). It was black expanding pond foam. I also used some coco coir I had around for the background.
https://www.amazon.com/Gal%C3%A1pagos-05213-Terrarium-Sphagnum-Natural/dp/B00KZDT346
I use this and it works great!
if it helps, this is the moss I got https://www.amazon.com/gp/product/B00KZDT346/ref=ask_ql_qh_dp_hza
More substrate. You can add it slowly & gently, about an inch at a time while they're down.
Heat source - you canpurchase a heating pad for cheap and stick it to the side/back of the tank (not underneath)
Deeper pools - salt & fresh you want them deep enough for your largest crab to fully submerge in but easy enough for the smallest to climb out of. Food storage containers are cheap pools and craft mesh works well for ladders.
Reptivines are great decor and provide climbing and hiding opportunities.
Additional hides - having multiple hides help prevent territory fights. I have a couple of terracotta plant pots turned on their sides and stuffed with moss to help with humidity
Additional levels - you can create more space by adding shower shelves or similar - mine are moss pits and include foraging opportunities
Foraging - I have urchin shells stuffed with foraging mix stashed around the tank - moss shelves.
Shells - you can never have too many. They should be size appropriate and larger... turbo shells are pretty popular with most land hermies. Shell opening measurement is what you want to pay attention to. You look like you've got a decent collection of appropriate shells(depending on your crabs size)
Honestly though you look like you're off to a great start with a solid foundational set up. Beyond deeper substrate and pools everything else is gravy.