I can provide digital images from Archdiocese of Chicago marriage registers before 1916 if you've found a license that lists a Catholic marriage or an entry in the PGSA marriage index.
The church records usually give the names of the witnesses, and in a few cases they may give parent names. (Many of the Polish parishes seem to have used registers that asked for parent names.) If you want me to check a particular parish to see what information they were recording before you request a lookup, just ask.
Please note: Occasionally the registers are very dark on the film, making it hard to get a clean copy. In those cases I will do my best to make the pages readable.
Fee if I find the record you requested: $7.00
Fee if I don’t find the record after a thorough search: $0.00