Essences don't exist in Wii MySims. The Essence system (mood-influencing decor) debuted in The Sims 3 (2009) and expanded in The Sims 4.
Wii MySims (2007) uses the original The Sims build mode: walls, floors, doors, windows, furniture, decorations, landscaping (trees, flowers, paths). No essence mechanics, no mood aura radius.
Creative freedom exists within the toolset—just no Essences.