Blast from the past! Here is the 1980s DC Comics Style Guide, featuring the art of José Luis García-López. This included not just guidelines for artists but also for marketing and licensing teams, bringing all character designs roughly in line. Check the rest of it out on José Luis García-López’s facebook page.
The late Dick Giordano inked all of the figures in the original guide, while Todd Klein inked all of the logos and many of the backgrounds. OpenCulture goes into the details:
Being 33 years old, this particular style guide doesn’t perfectly reflect the way all of DC’s superheroes look today, what with the aesthetic changes made to keep them hip year on year. But you’ll notice that, while fashions tend to have their way with the more minor characters (longtime DC fans especially lament the headband and big hair this style guide inflicted upon Supergirl), the major ones still look, on the whole, pretty much the same. Sure, Superman has the strength and the flight, Batman has the wealth and the vast armory of high-tech crime-fighting tools, and Wonder Woman can do pretty much anything, but all those abilities pale in comparison to the sheer power of their design.