Under Stair Cave for Dog

I have a border collie and catahoula. We opened up the drywall under our stairs and made a "dog cave" for our border collie which he loves. It's about 8' long by 4' wide, with an elevated dog bed and a nice foam mat on top of the elevated bed.

We had a plumbing leak and had to tear up the walls around his cave. He's been pretty unhappy and restless but the walls will come up in the next few weeks.

Any suggestions on improvements to his dog cave while it's open? Thanks so much.