I've used stones before to look at my family relationships. I like stones because you can touch them and feel them and you can either do it intuitively or deliberately pick stones with features that you think fit different people.

I didn't talk to the stones - it was more a conversation about how I'd arranged them and why I'd chosen each stone. Pretty enlightening actually but not the same as you're saying.

Some therapists use an empty chair so you don't need to think of an object - I personally find that kind of work quite difficult as I feel quite vulnerable and not that safe.

I agree that being able to pick your own object might work better. Gives you much more ownership and control over the process. And of course, you don't have to do it if it doesn't feel helpful or therapeutic. Different techniques work better for different people.