I think I would have one wall of saddles and bridles/headstalls
Then have a shelf underneath and have bins with your polo wraps, saddle pads/blankets/boots are kept
Have a chest full of vet stuff
Have all your driving stuff (harnesses) on another wall.. and then your grain can snuggle somewhere so it's not in the way.
Brushes you can just keep a little tackbox with that kind of stuff.
Let me see if I can draw it on paint..
Also keep in mind idk what your space actually looks like.. so made an educated guess.
The shelves are underneath the saddle and bridle racks, and there is one on the wall next to one of the doors. Storage trunks under the shelves but you can also put stuff on the shelves.
Big green circle is grain barrel and the blue thing is drawer for supplements (like smartpak has)