That bunny house is fantastic! We made ours the same way with the grates, but ours isn't nearly as tall. We got them a 'dig box' (a covered litter box) so our girl would quit using their actual litter box for digging--very messy! They ended up using the dig box as a 'shelf' to perch on so we never ended up adding the shelf we planned. My bunns love slinkies, too
Also, we like to hang baby toys like plastic keys and links from the top for playing. Our bunns aren't allowed free run of the house-- too mischievous! They are out most of the day, but they love their own little home. Also, my boyfriend now makes an adventure area next to their home with extra grates and cardboard pieces. He changes it every week or two so they always have a new challenge and a new area to remodel, Lizzie especially loves to add new doors and change the furniture around
Best thing we learned is to rotate their toys so they feel new and exciting!
Also, aside from some bunns just being more or less social naturally there are ways to bond more with them. Try visiting Rabbit.Org for all sorts of tips about caring for them. On the Colorado HRS site there are articles for playing and training bunnies. Of course, you can only encourage their behavior so far
My Lizzie DOES NOT tolerate being held very long- but she loves to sit and be scratched and loved. Her hus-bunn, Twitch, will run like hell and pretend he doesn't want to be pet, but once you put him in your lap he is butter, LOL. Also, to people looking at bunns, remember it is almost always essential to have at least two bunnies, they need their own kind to be content and happy
Haha, I hope this information helps somebody
Again, I absolutely love the house, I'm going to look into changing ours to be taller like yours. Thanks!