Alas, I'm a few thousand miles short of becoming a valued customer.
Now, hopefully, you're wondering about that last 10%: It's point 2 in your "How it works":
> Pack your things carefully and take pictures of the contents.
I'm sure legal would have a word or two to say about that, but: how much would it set me back if you did that, together with providing a rough description of the box' contents? This, then, would appear on my account page's List of Boxes.
The details are devilish, of course, and supreme caution is indicated: you don't want a prominent "take-a-peek" option to adversely affect the trust of your more privacy-conscious clients.
[0] Which, incidentally, doesn't appeal to me, as I am solidly in the tarsnap aesthetics camp, but we both know what to make of that.