When these art have been added it is really confusing even more so than the old single plant representations for the biomes. Must say I much preferred the old single plant reps but some updates can be;
Dessert: saguaro cactus instead of the joshua tree since cacti are easily identifiable in such a small pic.
Tropical: a coconut palm could be a better choice since as is I confuse it with temperate and mostly coastal biome; these three are too similar to each other at a distance. Also coconut palms are widely known as the tropical plant in popular culture I suppose.
Coastal: like in the tropical pic some sword ferns can/should be added to bottom sides as it is the main reason I think I confuse it with the tropical biome. This can also help with differentiating with the boreal biome more.