I've got an A20-4GB running Android from the NAND flash. The wiki mentions change_display_A20_OLinuXino.sh on this page - https://www.olimex.com/wiki/A20-OLinuXino-MICRO#How_to_change_HDMI.2C_VGA_and_LCD_resolutions.3F - but apparently that's only for the SD image - it's not there on the NAND.
Hmmm ... just booted off an Android SD card and it's not there either. Any suggestions?
Your only real option is to build the source and configure it, as you will have seen from our other discussions, for Android this is the only way. It's not really designed to change on the fly as it is supposed to be on a fix display device.
I have it all building now and have already created a custom build with a nice boot animation etc. Still trying to get SMS working, but it wasn't working in the current image anyway.
If you have a machine running Ubuntu and configured for Android building, I am busy uploading the Kernel and Android4.2 source that I have working. It has a few custom items but is basically stock in the version I will upload so you can build your own and change the display to suit.
It will take a day or so to do this so I'll post a link the source on my blog once it is up and I'll detail the changes for those who want to make it their own. :)