Currently, we do live in a house that has a room that was built purposefully as an office. It's a bit smaller than I would like, but since I'm only homeschooling two out of my three boys, we are able to get everything into this room, with some careful organization. My oldest son's desk is in a different room, what we dubbed the "library", what is supposed to be the formal dining room which we have no use for, so it had several bookcases full of books at one point. I've been able to reduce the number of books and organize so all of our books are now in the homeschool room, but we do have a few things in the library, so it's a good quiet place for my oldest to do school work.

I went with a black and white theme in our school room. I like that it offers simple and clean lines. We have our "pop" of color from various art work that will be hung throughout our school year, as well as maps of the U.S. and World by each desk. The wall is currently white, because we rent, and my hubby refuses to paint anymore. White would not be my color of choice, but it is what it is for now.
Each boy has a desk, along with a pencil cup (attached to the wall), a metal circle on the wall to hang personal items with magnets, as well as a desk lamp. All from Ikea. The desk shelving does not have a drawer (it's a shelf, that holds their subject binders) so behind their chairs are drawer systems (which we had previously used with the Workbox System...we no longer do that system so it's a re-purpose for the drawers). The drawers hold their markers, colored pencils, art pastels, crayons. Each drawer holds one type of item...I love that organization!
I have three Ikea Expedit bookcases. They are like cubbies. I love these better than a regular bookcase with long shelves, because you don't have to worry so much about books falling down since it's easier to fill up the cubby, versus a long shelf. Unlike other brands of cubby systems, Expedits offer big cubbies, over 12 inches in height, so even binders can stand up in them. Plus I think the Expedits offer a bit more style in their design than the cheap cubby systems sold at Walmart/Target, etc. I have one Expedit that is a double, so two rows side by side. This is between the desks of my boys, and where all of the curriculum we will use this year is kept. I also have two taller single Expedits, so just one row of cubbies. These keep our collection of books, the ones for future use, and just fun reading.
My desk is also from Ikea. I went with a gray desktop, just to change it up a bit. I went with a drawer system for my desk, instead of the shelf system the boys have. Love these drawers...deep and hold so much stuff!
I've purged, cleaned, and organized the room all throughout the month of June and into July. I was thinking it was ready to rock and roll...but I was hating the big space of blank wall above the desk area. It was too high to be useful for something like a map, my boys wouldn't be tall enough to see it. Hmm, what to do...what to do. I went with vinyl wall stickers. Black circles of different sizes. I put those randomly across the top of the wall and I love the visual in the room!
I do love our homeschool room and it makes me smile every time I walk in.
NOTE: I've just got to address this. Over the years, I've had other homeschoolers say to me "Oh, my child could NEVER sit at a desk all day long...we just prefer to sit on the couch or he likes to lay on the floor...just wherever he's comfortable is where we do school!".....as if implying that my children sit at a desk, from 8a-3p, never getting up to stretch, etc. So just to share, we also do school all over the house. We sit on the couch, my boys roll around on the floor, we lay in bed (usually when we are reading), we go to the pool, we lay on the trampoline, we use the kitchen counter...you name it, it's fair game for school time. So we are not locked into our homeschool room all day, every day. BUT we do have table work. Work like handwriting, map labeling, composition, etc. This type of stuff requires a hard surface to write. So we go into the classroom to do that stuff. Then we go out to do other stuff, then we come back in if need be. So believe me, we are on the move all day long. I can't imagine those families that "wherever he's comfortable is where we do school" are able to completely avoid migrating to a table at some point in their day when a hard surface is needed for writing. There, got that off my chest, lol!
So here's my big debut! Our school room, for 203-2014: