How about really inserting a picture at the beginning of every paragraph but just change its contents with the macros like \RedBox, \GreenCircle and so on?
% Some random definitions which may or may not contain whitespace or newlines
The following example updates \mychapter by doing the following:
Store the second argument #2 in a command called \chaptoc.
Use regexpatch's \xpatchcmd* to replace all occurrences of \\ with nothing (effectively removing them)
Use \chaptoc as the addition to the ToC, while printing the original chapter title as part of \chapter*.