Holy Crap you've got a lot of stuff what do you want more for? You don't need no more. You got heaps. Stop buying stuff and start working out.
You're only 13? is that a typo?
Man I wish I had that when I was 13. I doubt half those manufacturers existed back then.
Get another weights tree and some more plates. I like the plates with holes in them, the ones with you know, kind of "handles" you can attach them to stuff e.g ropes, and pullem up by the ropes. Or a Metolious grip thingy.
Get a bigger clock. And get two stopwatch countdown things you can program to go off say in 2 minutes or 3 minutes. And a metronome wouldn't go astray if you is really fussy about timing.
Put another mirror behind your cage.
A trapbar for deadlifts isn't a bad thing. If you are looking for things to spend money on.
I don't see a sandbag, and that would be a nice addition.
If it were my gym I would add a punching bag and some double end / speedballs etc..
Geez man get some posters! Especially some red ones, the colour red helps you get stronger by making you more angry, like.
And a sound system
You could also buy some powerbands. You probably don't need them but personally I like them. Actually, chains might be good too. But these are more advanced things and not that important.
Far out I forgot, medicine balls.
Also if I had that room, there would be a second power rack on the other side of the room, and the two would be joined by beams, from which I would have a monkey bar system of holds, bars, everything you can grab and swing from, and one power rack would have squats setup permanent, the other, something else, also permanent.
But really you don't need to add anything, what you have got is plenty, now use it. Really at 13 all you need is a barbell.