We seem to have a few issues under discussion at the same time here, and I think it would be helpful to separate them.   

Maintaining "old" FAs
As  said (00:14, 11 December 2008), this article was promoted to FA in 2006, when standards were less demanding, so work is needing to keep it close to current FA standard.

Unfortunately the "committee" process advocated by  doesn't work if the "committee" is slow to respond. In Oct 2006 I pointed out some serious scientific errors in Dinosaur, another "old" FA; nothing happened so in Jan 2007 I gave notice of my intention to fix these points; a few days later, after nobody objected, I fixed them; and a few days later the corrections were reverted, so that the article again contained the errors I'd pointed out 3 months earlier.    

Quality of images
This one has the potential to run for a long time. I have no strong objections to the image per se, but I'm not sure the article needs a reconstruction of a juvenile T rex'.   

Selection of images
Wikipedia is not a picture gallery, and images need to be used selectively. IMO if we have have plenty of images, as we appear to for dinosaurs, we  should use those that illustrate the content rather than just providing eye-candy. In many cases diagrams should take priority over pure pictures.   

Size and placement of images
There has been recent disussion of this at Wikipedia talk:Manual of Style#Forcing Lead image (plus a more general Wikipedia talk:Manual of Style item that's now archived and I can't find it) and at Wikipedia talk:Accessibility#Image position. To sum up my own views:
Images that illustrate specific content should be alongside that content.
Layout of pages that use images has become more difficult as widescreen monitors have become more prevalent, as increasing the text width reduces the height of paragraphs, sections, etc.
I dislike left-floating images, as this makes the text less readable by changing the postion of the start of the next line, so that users have to search for it rather than jump to a familiar X co-ordinate.
The functions of images vary. Sometimes they convey a lot of detailed info, and a larger size than the default is needed. On other occasions they need give only a general impression of what something looks like, and a smaller size than the default is adequate. The majority of readers are unregistered and therefore cannot set preferences for image size or anything else. Hence editors have to pick image sizes that are appropriate for the purpose.
Accessibility to users with poor vision (but not functionally blind) is irrelevant, as they will either have their browsers set permanently on "zoom in" or have software that zooms in for all apps.
 makes ugly gaps in the text and reduces the readability of articles.
IMO all these points indicate that MOS cannot dictate a "one size fits all" solution and editors should be free to set image sizes.