I love pattern illustrations. The fine details in the drawings - the perfect hair, dainty shoes and the fabric choices all give me lots of ideas! Making wool look like wool with tiny little brush flecks is always fun to see.
Sometime the models can be a bit suspect or being doing some very odd poses - take a look a pattern junkie if you need a good giggle!
There are of course obvious issues with the illustrations - the models legs can sometimes be a little unrealistic and some illustrations for plus size women are still drawn with the same template as the misses patterns - but that's a whole other kettle of fish that we might discuss another time. As un-PC as they are, it definitely shows how far we have come to be more accepting of other body shapes.
My favourite years to look at are mostly 1967 to 1968 patterns, but I decided recently to look at earlier years and compare how the styles have changed through the decade.