I could be wrong but as I understand it, Golden Age = creation - 60's. Silver Age = 60's & 70's, and Modern era would be 80's+.
Golden Age is anything until about the early 50s.
Silver Age usually has an unofficial starting point of mid 50s until 1970
Bronze Age is 1970 until 1985
Modern Age is 1985 until present.
So what does that mean? Not artist specific as SSC has already shown that with their PFs they are starting with a base and then moving around from there into something idealized, but the overall looks for the characters.
So Batman for example:
Golden Age (short ears, no oval, boxy physique):
Silver Age (oval, heavy black highlights, introduction of the "capsule belt"):
Bronze Age (tall ears, less highlights throughout, slimmer more athletic build):
Modern Age (this one is rough because it spans 27 years and he has had so many looks within this one time span but I would bet they are looking at this because the black was used more than the blue before Jim Lee's Hush):
New 52 (or they call it Justice League which has the lines, the mesh under the arms, stylized gloves, boots):
I think you'll see artist specific for ones that are popular but way out there like Frank Miller's Dark Knight Returns but with popular artists like Neil Adams in the 1970s Bronze Age look which is also referred to as the "Classic" look because the Bronze Age looks for a lot of heroes lasted far into the Modern time.
