Expand upon what you already have - Freshome.com

In many homes, you already have the ‘bones’ for a good playroom.  Consider using main walls of your living room or dining room that have plenty of space for kids to be imaginative with.  Wide open walls can be used for bulletin boards, lining up easels for art projects, or for blackboard magnetic wallpaper for the ultimate in non-stop creativity for your kids. If you are handy with do it yourself projects, consider building built-ins for desks for adults and children to utilize while other family members are using the wall chalkboard.