Hang guitars on the walls as a functional style of decoration. Nearly every guitar store sells a variety of guitar stands. Some stands can be mounted directly onto walls and hold guitars by their headstocks. Adding these stands around your guitar studio will not only allow you to display your instruments, but also give you quick access to your guitars. If you're a serious guitar player, you may use several instruments tuned in a variety of ways. With hanging stands, your guitars are always within reach.
Mount posters of your favorite musicians or bands around the studio as inspiration. Recording an album can be a long, arduous process. It may serve as motivation to be able to occasionally look up at the poster of a successful recording artist and know that if you work hard, you could one day enjoy fame and success, too.
Display personal music-related awards throughout the studio. If you performed on an album that went gold or played a live show at a celebrated venue, display that gold plaque or concert poster to remind yourself to continue working hard. Celebrating your own successes in music will encourage you to continue making quality music.
Affix guitar-related charts to the area in which you play as a quick reference. These charts can include chord charts, scale charts and tuning charts. While all this information is available online and you may have committed much of it to memory, having ready access to these charts is an asset.
Add any other pictures, decorations or mementos that make you feel comfortable and relaxed. The studio shouldn't necessarily feel like home; if that's the case, you might not get enough work done. But you want the environment to be comfortable enough that you can be creative. If you need a photo of a loved one, a favorite couch or other household item, include it in the studio.