There are a lot of books and mag articles on such a topic, and I have come across lots of features in my years of taking too many magazine subscriptions, so you might browse a bookstore or search the net for great photos. The closet might be able to be outfitted as the actual "office," if you use the right doors and really outfit the inside. There are lots of decor features on that approach. That is more important, I think, if you and your nuclear family want to use the room more often as a cozy library/study and can then close the doors on printer, FAX, etc. but also is a great way to maximize floor space, since you can use a closet as an "indent" in a room for office equipement and desk, but can't sleep in the closet! Sofa bed vs. Murphy bed can be space-saving. There are furniture lines for installing Murphy bed and associated cabinetry. This approach is more for if you yourself don't need the sofa and want to preserve more floor space and a clean-lined look. Otherwise, a compact sofa bed would serve you and your family for library. Shelving is key and you should be prepared to design and install it so that it works for you--(or have done professionally). That goes for the whole room--by that I mean, draw your floorplan and wall views with windows, doors and really brainstorm on different ways to use the space. For example, you might be able to surround a sofa bed with built in shelves floor to ceiling for a great library look, whereas a lot of free-standing shelves would take up space. Or, you might be able to find free-standing shelf units you can pair and connect with a bridge. Lots of ideas like that. Of course you have a budget, but try to think outside the box and be prepared to buy a new item if it will really make the space work better--so if your current file cabinet doesn't work well, you might budget for one that fits better or is more streamlined, or maybe you need 2 matching and put over them a desk top. As in first paragraph, there are huge numbers of ideas on multi-tasking furniture for these purposes--file cab as bedside table or under a table top and skirt; rolling file or printer stand that rolls under desk top; storage containers that might let you "remove" a few items temporarily when guest using the room and needs place for luggage, and return later.

I have always had many, many guests: professional friends who may stay across a weekend, university students who come for a meal, or, in times past, lived at my house. I have pretty things, and I have taught dozens of young women how to take care of porcelain, crystal and silver (no, don't scrub it with a scrubbing pad...). Almost all people are respectful of other people's things and if I see something I don't like going on, I feel very comfortable telling them to cease and desist. If someone's children decide to bounce on the sofa, I just scoop them up and put them somewhere else. The biggest problem for those of us with old furniture that doesn't have bulletproof finishes is water marks. I have to patrol a little bit at a party to make sure people are using coasters and not leaving wet marks on the tables. Same goes for house guests: " make sure you don't put your wet towels on the back of wooden chairs--use this rack instead." I found the comment about books being somewhat private to be the oddest of the odd....I'm of the other persuasion. People with big book cabinets filled with a cookbook or two and a lot of "filler" are weird to me--with the obvious implication that the owners are among of the college-educated persons who, upon graduation, never read another book. What's the percentage? I forgot, but something very high, like 75%.

You really need to find a home for all the books unless you use them all , all the time. Right now that room is no where I would like to sleep. IMO cover the fireplace with the murphy bed in fact you can even get one that incorporates an office . IMO this could be an office and a guest room and forget the den idea, Ilove books but IMO most info can now be found online and in a small space actual bookcases take up too much room this murphy allows some book storage a desk for you to work on and nice place for guests to sleep . Honestly in this small space I think that is all I would do. Or a sleeper and a desk maybe use a closet for other storage guests really require very small closet space

Regardless of forever home or not it would make sense to utilize the closet better for all of your 'office' stuff so if that means getting an outlet put in there so the printer and all your stuff on the tall shelving can go in there - that would be wise. Then, daybed or not, replace the tall shelving and nightstand with a continuous low closed storage furniture piece - maybe like this photo - this will open up the room visually. This furniture piece can function as a nightstand and office storage. Closed storage is your friend in this space. Replacing the closet doors with slider doors would allow for the 'office' to function easier. Maybe the inside of the closet is converted to half 'closet' for guests use and half 'office' with shelves for printer and office supplies. Then, once you decide on daybed or not I'd repost an updated photo and we can help with rearranging art. I think where you have it now is not doing the room any justice. I could see it consolidated/edited on the wall where the tall shelving is as that will create a focal point.