There are various options.
- Go to System -> Factory Reset. This should give you the image back that you used for your first install.
- If that would set you back way more than you want, there is currently -to my knowledge- only one other route available: go to Github and compile and build the image you want, from the source. This route requires you to be familiar with Linux but it will produce what you want. Eventually.
There used to be a whole set of images available, but they have disappeared a while back, see my post of November 2nd. Regretfully, these are still not available and have as yet an unknown ETA.