Add music, keep your favorite CD selection at hand, when your CD ROM is not in use for graphics or other software program, play your favorite music... it beats sitting in silence and listening to your CPU's fan!  If your computer case and finances can support it, add a CD player specifically for music.

If your spouse or children are a motivating factor you should keep photos around your room to remind you when you are discouraged the reason(s) you are working at this.  If your goal is to travel or purchase property or a vehicle from your profits it's a good idea to place posters around your room to remind you of your goal.  Make your work space uniquely yours by surrounding yourself with images and objects that are distinct to your personality and interests... a stringent and stark office is a horrible place to spend prolonged hours, unless you like the institutional look.  Place objects all around your office area, use them as an eye-break to permit your eyes to focus at a different focal point to prevent eye-fatigue.

This is your office space and you are the boss, there are no stuffy rules and requirements where your office decor is concerned, it's truly yours to do with as you please.  The objective is to achieve a space that you look forward to using.  If you are a sci-fi fan and want to be surrounded by aliens and galactic art, it is perfectly acceptable decor for a home office... once again, think about some of the decorated cubicle spaces seen in other productive offices, and the most productive offices are the ones that permit staff to add those personal touches of self-amuzement to their work space.