When I was an audit manager I never had a problem with the fact that tickmarks might be inconsistent from audit to audit. What I didn't want to see was inconsistency within the same audit. We required that one of the initial workpapers in the file be a legend of standard tickmarks and their meaning. Any additional tickmarks used on a particular workpaper had to have a legend on that workpaper explaining the tickmark. Some pretty basic ones you probably don't want to deviate from - for example a check mark means everything is OK and an X means there is a problem. Although you could reverse those by use of a proper legend, to do so would be very confusing for anyone reviewing the file, so would probably not be recommended.
Jim Bedsole, CRCM, CBA, CFSA, CAFP
My posts - my opinions