Old wooden Scrabble tile racks make great display shelves. Present & Correct suggests simply gluing the racks onto walls. To hold items that are heavier than game tiles or lightweight books, racks may.
(Ideas to create your own Lego advent countdown) Five Christmas LEGO Projects to Build - With Instructions! Train ornament, nativity set, snowflake ornament, Rudolph, and cube ornament. The post has links to more Christmas ideas too.