How I missed the option for registration, I can't say. I was blind, I guess :) thank you.
But this compression option... it requires me to create image placeholder, so to say, and configure upload options just for that image, and then in 'on demand upload' select existing image...?
But those defaults must exist somewhere, as they are applied to on demand job which isn't preset in web interface.
We are using on demand exclusively, just selecting and dropping images onto machines. Images are syspreped, so we don't need anything than selection of the type of machine and dropping image there.