DS was moved to a bed at 13 months from our bed (altho he still spent majority of the time in our bed lol) and he was used to being between our pillows, so I had a pillow in his bed for him to be next to. But even now at 22 months he doesn't sleep ON the pillow, it's still just next to him

I think it's not recommended to use a pillow before 12 months, but you will probably find they won't use it anyway because they're used to lying flat.