I followed YAGM installation instructions and installed all modules the modules that YAGM depends on. I also made sure Image module is not installed. Still, when I installed YAGM I got this message:
"An illegal choice has been detected. Please contact the site administrator." Well, I'm the administrator :-) so I have nobody else to contact and since this message is so "informative" I have no clue what went wrong.
Other messages say this:

* Created field Image.
* There are no fields configured for this content type.
* The content fields table content_type_gallery has been created.
* The configuration options have been saved.