The reason I included this shot is not because I think you have a lot of jars full of shelves, but because of the way the room borrows light from the other room through the translucent wall.
Buying coordinated organizing accessories will help keep things looking professional. IKEA, The Container Store, and West Elm have great file boxes, magazine files, baskets, etc.
These cabinets can hide a multitude of messy sins. Often times they hide outlets as well. Keeping things neat and organized is key. Also, check out the long desk. Instead of having so many drawer cabinets, you could create several work stations along the surface, with wiring hidden at each one. You do not want a bunch of surge protectors and a tangle of cords all over your floor.
I feel like this office could work really well for you. It utilizes each wall to the maximum with a large, U-Shaped desk. Note how one wall has storage, one has inspiration boards, and one has windows. This is a great way to organize this guestroom-sized space.
This open office is divided into areas for different purposes: Meeting, drafting, library, and storage. Think about anything you'll need to store. In this case, blueprints are large and require flat files and deep cubbies.
This is just a great example of a spare, organized, and professional home office. It's also a good example of what to do with a long, linear space.
Again, a way to maximize a long, narrow space.
The least expensive yet very attractive file boxes I've ever found are these white ones from IKEA. They keep things from looking cluttered.
If some of your office space is more integrated into your home, or you need to maximize a small space, consider a unit like this where you can shove everything to the back and make it all go away during your off-hours!
This setup allows two people to work in a small space.
A library aesthetic can also be attractive in a home office. Obviously, this person has a lot of space, but if you do have a whole floor to work with, consider a large table or two away from the desks where you can spread out or have conferences.
All the matchy-matchy keeps this looking professional - same counters, same lamps, same chairs. When you're working in a small space, keeping things coordinated goes a long way.
Keyboard shelves help keep surfaces more clear. Sometimes a big behemoth of a desktop computer hogs up way too much of the actual desktop. If you are buying new computers, work with the salesperson to minimize the electronic bulk in your office.
I included this one because when I said "separate building" you likely thought "yeah right," then thought about the garage, then thought, "nah, too impossible. I'll be like George Costanza pretending to sell computers with Lloyd Braun in his father's garage". However, check out the amazing door on this one. It's worth looking at the garage with fresh eyes. It could lead the way to "Serenity Now, Serenity Now!" (I apologize to those who don't share my Seinfeld memory for this comment).