This brings up an important point:
The game needs invasions. No extra graphics would be needed; just reuse the envoy as a troop transport. While your troops are invading, you see explosions rage across the planet's surface.
Add in planet-based weapons systems, and invasions might sometimes be preferable to nuking from orbit as your troops struggle to take over the enemy installations. As the fleet battle rages overhead, you try and drop as many troops as possible to turn the tide of the battle. The bigger the planet's pop, the bigger the militia there, so send in lots more transports!
Then again, nuking from orbit *never* gets old, why is that?