I'm about to stuff some of my water loving orchids in there. Love seeing what's being done here. Moss falls. <3
Suggestions: Pothos cuttings, Sweet potato cuttings, wet ferns (I have my maidenhair fern in there). Really, it's anything you can cut and root in water. I could stick my rooted avocado pit in there. I have so many random things in water culture, they'd do fine in the HOB. I'd love to try Sarracenia one day
For more terrestrial plants like the fern, I stuff them in a net pot with floss and then sink just the bottom of the pot leaving the rest above, it keeps the whole thing moist just by capillary action and doesn't drown the poor plant.
The biggest trouble I'm running into with water culture is that my plants aren't as hardy as they could be being a bit short on nutrients, so when a pest hits, it hits hard. I just had to throw out my entire pile of sweet potato cuttings due to spider mites infestation. It's Spring. All the bugs are out in force.