I don't know how. I usually turn off "image display" when in 3g. If i change from 3g to wifi, "image display" automatic turn on. So i hope opera mini can do it too.

I have 2 suggestions:

1. Night Mode: Because many people often use Opera Mini when they are in dark (bedtime, lights out....). So it help us to protect our eyes.
2. Auto image quality changing: If enabled, Image Quality auto changes when we use data (off) or wifi (high or low or whatever users choose).
   I don't remember how many times and how long i wrote this suggestions and email for opera But nothing changes. I hope you won't let me down again.