Eco-living could be a great chance to expand plant options - basically new ways to grow them. Plants could be trained up walls for example to save space, or grown in pods that cultivate them for you with less work and produce more food too. I guess a way to integrate plants differently in to gameplay, not just the traditional put them in the soil/pot in the garden way.
I also like the idea of resource saving to reduce bills. Solar panels and wind turbines are obvious I guess, but how about water saving toilets and showers that reduce bills a bit.
