MAKmak Beta thread. - Just a fun project me and zip worked on that used VERGE to open old CHR files and almost any image files, which were then exported to files that chrmak5.exe could handle (a BAT file, and a BMP).
VOpenCHR. - allows editing of all CHR formats.
Have fun with these links. These tools are your best friend. The packaged command line conversion tool is not quite so.
EDIT: Added the above mentioned links into the CHRMAK5 documentation, so that other new people can benefit easily, as well.