We did 3 months of stall rest last summer with a torn ligament.
We bought him large blow up balls - he did destroy the first one and needed another one but then we just started buying the $ 9.99 ones at Wallmart and let him destory it, patch it up when we could and use another when it was totally out of comission.
He started out with a couple of weeks stall rest, then we moved him outside to a small pen the size of a stall, he did much better outside as he could look around, see the other horses etc. And get some sunshine which would be needed even more while he was trying to heal.
I went out and just visited with him most days and brushed him, which helped to give him something to do. He was near the house so I would go out on the deck and talk to him just to give him something to occupy his time.
We also used essential oils to calm him and help keep his mind good - pm if you want more info. here.
He actually got a little better as time went on, he just kind of accepted the whole thing. After 2 months we gradually increased the size of his pen a panel at a time so that he could move around a bit more but not too much. Eventually we went to hand walking etc. He wasn't perfect and hand walking was bit of a challenge but we did get through it.