This is my wishlist for Swarm updates or later geodefense games.

1. Level 8 towers, either with new mechanics or just more range/power.

2. Tower damage specs: It is difficult to develop strategies without knowing exactly what kind of damage different towers do at different levels.  This should be listed along with the other tower specs.

3. Creep health specs:  I want to know how many hit points a creep has, either just to start with (level 4 creeps have 10 hit points, etc.) or if I click on the creep I see that creeps specs.

4. Score bonuses for starting levels early.

5. A button which toggles towers to stop firing.

6. Different styles of gameplay, like an action mode where killing creeps faster gives score or money bonuses, or gambling on creeps which for a new round have more hit points or move faster, giving score bonuses or cash.

7. Towers which can be placed on tiles that creeps cross over.

8. Larger maps with scrolling.

9. Custom map making and sharing.

10.  Multiplayer gameplay.

That's all I can think of now.