first, define "more modern look" - what, for you, appears
archaic on the current look and feel offered in a chm?
keep in mind also, that changes to look and feel can add a
serious amount of anxiety for your end user. sometimes consistency
(even to a boring point) is a good thing. if I am a user looking
for help, the last thing I want to wade through are a lot of bells
and whistles that get in the way of the information I need.