Where are his toiletries? Stuff for the kitchen? more socks? everyday bag as opposed to that travelling one? a single book he's reading right now, or a reader like a kindle or whatever?
This guy doesnt't look like he's actually living with 15 things, which makes the point kind of moot. He doesn't even have a towel.
Let alone anything like a dress shoes.
I don't think it's possible to get ownership down to 15 things.
Each of the following is an absolutely minimal thing:
1) laptop
2) power adaptor for laptop
3) phone
4) power adapter for phone
5) toothbrush
6) toothpaste
7) underwear
8) underwear
9) underwear
10) pair of socks
11) pair of socks
12) pair of socks
13) shoes
14) jeans
15) jeans
16) everyday bag
17) towel
18) bodywash/shampoo/and shaving cream in one
19) which reminds me: razer BZZZZZZZT over the 15 :) and you're just getting around to being able to shave.
20) shirt
21) shirt
22) shirt
23) sweater
24) sweater
If you add some moisterizing cream and maybe a watch and blazer, maybe a second pair of shoes, you're pretty well set though to move to a new city. You don't need a wallet, that's why jeans have pockets. a belt wouldn't kill you either.