Dolls don't usually have brand marking stamped on their bodies, so I'm not sure what you mean or how you plan to make them "generic."
If your illustrations look so much like a branded well-known doll that they're consumers could be confused as to the source of your illustrations, then you're probably infringing on that doll's rightsholder's trademark rights.
Likewise, if your illustrations look so much like the branded well-known dolls that the images are substantially similar, then you're probably infringing on that doll's rightsholder's copyright rights.
In addition, if this book treads on the markets of these dolls because their rightsholders also publish books, then you're probably unfairly competing with their IP rights.
In sum, because almost all questions about whether a questioner's use is an infringement depend on the other uses compared with the questioner's intended use, you need to see an IP lawyer to run all this by them and get some specific advice.
Disclaimer: Please note that this answer does not constitute legal advice, and should not be relied on, since each state has different laws, each situation is fact specific, and it is impossible to evaluate a legal problem without a comprehensive consultation and review of all the facts and documents at issue. This answer does not create an attorney-client relationship.
What Ms. Kosyln said.
I understand your question to mean, however, that you want to publish photographs of dolls in your book. If so, the rule is that you can only use a photograph that you take or have licensed from the owner of the copyright in the photograph. If the "images" that you're referring to are drawings, the same rule applies: you can only use your own or those you have licensed.
Assuming you have "cleared the rights" to the photographs and/or drawings (because you either created them yourself or have licensed them) the question as to whether it's lawful to publish them turns on many factors which must be evaluated separately for each image: the theme and purpose of your book, the role the photograph plays in the book, the "fame" of the doll shown in the photograph, the role the doll plays (if any) in the book, etc.
For example, you cannot lawfully publish a book that tells the story of a Barbie army fighting off an army of Dam troll dolls and include photographs and/or drawings of Barbies and Dam troll dolls. There are lots of other instances where such publications would be unlawful. You need to tell an intellectual property attorney your plan and get his or her opinion. Good luck.
This is a very fact-specific inquiry. The answer will be, as said above, dependent on how you intend to use the images, what you mean by "images" and "generic," what rights may be protected in the respective dolls, and a host of other factors. You will need to talk to a lawyer and lay out both your concept and, in all probability, arrange to have the publication vetted (reviewed in advance) to protect yourself, as well as to persuade any publisher to even consider getting near the book. Good luck!