Everyone at my barn also has their own 'box' they supply. I do have a regular trunk I picked up on craigslist for $50 that I use across from my stall for storing blankets and odds and ends. But the tack 'boxes' are in a separate tacking up area at my barn.
I bought this TV armoire on craigslist for $100. We removed the shelves inside (only had to bang one out, rest were the adjustable kind) and added plywood on the back for reinforcement. I already had the saddle racks - which are just the plastic covered metal kind and bridle mounts and just bought a few extra double hooks at the hardware store. And added the lock setup on the front. It was only a couple hour project with the husband.
I only have one saddle, so the 2nd rack is for my pad. You could easily get a taller one for 2 saddles. The only difficulty was finding one with enough depth for a saddle since I didn't want to put it in sideways. But there's always tons on craigslist, you just have to be willing to call/email about dimensions since no one ever posts that.
The bucket in the back isn't there anymore, I have bottles (fly spray, shampoo, etc lined up along the back now so the purple tote fits in better. Also I store my 1/2 chaps to the left of the purple tote on the ground (not pictured). Because I don't run up my stirrups I had to organize around them so I could put my saddle in and out w/out hitting stuff :)
My paddock boots go in the blue 'basket' on the right and the basket below that houses odds and ends like sponges, hand towels, etc.
I should add I also have a toy box at home to store excess tack that I don't regularly use or was purchased not for this horse but still have kicking around. But if you had a bigger box, you could fit more stuff.