A good place to look for old pics... the Library of Congress' American Memory
http://memory.loc.gov/
Lots of stuff in there, old six day racers, etc.I see some older ads predating your timeframe in an initial look, but haven't evaluated every image they have on bicycles.
Peter ..................................... Peter Brueggeman La Jolla California USA pbrueggeman(AT)ucsd.edu
If anyone knows of any more sites with old (1900-1945) advertising, leaning more towards early American bikes, lightweight or otherwise please post. Thanks. Pete Geurds