Witch this instruction you can change your image for every wersion what you want.
1. you need android SDK from this website Android SDK | Android Developers
2. install this
3. after this you must run your tablet with connected cable to your PC on fastboot mode (vol button down and power)
4. chose USB icon on tablet (after this chose on your PC you must see "found new hardware" and founded drivers) if you have problem with USB drivers write information on this thread.
5. you need original upgrade file from asus website and after download, uncompress (need blob file)
6. found on your computer where you have installed SDK (find fastboot file)
7. on this directory copy blob file
8. rund cmd and write this: fastboot -i 0x0B05 flash system blob
9. after finish this (few minutes) you must see inforation "success"
10. on doos box write: fastboot -i 0x0B05 reboot
11. you finish your upgrade
12. sorry for my english