Highest I managed before quiting.
Storms are useless, Fires also useless.
Ice seems the only way (with a single tower) to survive the first waves.
Once that's complete, Nature towers can take over.
I did manage one game right before the above with only Ice towers and got to 71.
Has anyone bothered trying that $3000 tower on the lower right?
Seems as though it would be a better value than even Nature towers, but I don't know about the range.
Edit: Got bored and tried again.
Holy crap! That $3000 Flower tower is crazy!
The upgrade sucks ($5000 for 6000 more power and 10 less range), but the upgrade after that ($15000 for 900,000 power) is insane.
The only problem is collecting $15000 without dying.