You don't sit at this spot, do you? if no, get some matching lower cabinet w/doors (if you can) or do some custom shelving so you can store baskets or files or trays underneath the desk area. You could also find a file folder storage.

as for the top portion, right now it's crammed with too much. pare down what you can and find storage trays, boxes, etc for the other things.

why don't you visit The Container Store? They have tons of ideas and items that would work.

To make it nicer looking, remove the plant on top and find some nice, dark wicker baskets. Put some of your lesser used items in that and place those on top.

For the wall space, I'd repaint in dark, bold color, or find some peel and stick wallpaper to jazz it up a bit.

grab some new knobs while you're at it. Hobby Lobby has some nice ones.

You might consider a printer that has a fax element inclusive. That would eliminate one device.

Buy a raised printer stand that holds extra paper beneath it.

Remove everything from the cabinet for decluttering. Recycle the unused manuals. Use a clear shoebox instead of an old cardboard box to store miscellany. Don't buy any storage boxes you can't see into.

Dump out each drawer and go through its contents. You may find room for an extra ream of paper.

If the old plastic drawer chest is useful, put it under the fax machine. You may need a stand for the fax machine if the plastic chest is not sturdy enough to support the fax machine.

You could have another shelf made for inside that wall cabinet above the binders, and even add a shelf under the wall cabinet. Keep larger items on the big shelf, and put all of the smaller items together.

It appears that wall cabinet is deep. This creates a situation where we stuff things in the cabinet, 2-item deep, then we have to move the stuff in front to get to anything in the back. Anything you can do to keep the items in the cabinet 1-deep (or about 12" worth of space), will help you to find what you need.