So some context here, Monster Manual type books do not usually have handout-like sections in the print version while Adventures do have handout-like sections in the print version. Content Converters only convert what is in the content to a Roll20 format. They generally cannot create content. This is why in some adventures you will see some creatures with no image, just a "placeholder" token with the name of the creature. There was no image included in the adventure. Between these two things, this is the reason Monster Manual type content does not have that. With that said, I think an excellent suggestion would be to enable the Avatar (not token) to be displayed similar to how the token is (via Shift+Z). This would solve your problem. Alternately, as others have stated, you can display the Bio & Info tab. Many of those include an image. Just the text will need to be relocated to the GM section.