You can use red background for December, January, and February. That works for Chrustmas, and is bright for January. Then, it can work for Valentines day. A good basic color for spring is green. It can be used for spring decorations, and for Easter 4.
Any bright color is good for summer bulleting boards.
You can use wrapping paper as a background. Where to get ideas 1. Ideas are everywhere. Be on the lookout at all times. Use current events.