I'd select a theme that relates to you and then work with it from there.
For example, you could do a space theme. Make the background a dark blue color, and then pin planets in strategic places.
You could do animals and go as "cute" or a serious as you'd like. You could do a safari animal theme, or a cats and dogs theme, or something like that.
You could do a Victorian theme and cover the background in a Victorian-style wallpaper. Then frame the things that need to be hung on the board using lace in the shape of curtains.
You could go serious office theme and use die cuts of staplers, computers, and other office equipment.
You could go patriotic using stars and stripes.
You could even make a rock star theme and make the center in the shape of an electric guitar. Use neon colors and posters of musicians.
You can paint your bulletin board, or cover it with fabric, wallpaper, or even carpet! Can you imagine shag carpeting and fuzzy dice? It'd certainly be hilarious and yet eye-catching at the same time!