radical hacks Multiple View Calendar added a few things to WebCal, like an events list & thumbnail calendars, and some custom graphics, and have centralized a few of the variables which affect the appearance of the display which should make it a bit easier to modify to your tastes.
You can take a look at his demo Calendar, user comments or download the modified calendar.
Here are Chuck's installation docs...
To install the mods file:
1) Make a backup copy of your existing calendar.cgi. The tar file will overwrite it!
2) If you downloaded one of the comressed files, decompress it to extract the tar file. If you downloaded the zip file, unzip it and skip step 4.
3) Place the calendar.mods.tar (or calendar.mods.zip) file at the top level of your Calendar directory with your BACKUP copy of the calendar.cgi.
4) Un-tar the calendar.mods.tar file, or unzip the zip file. On a UNIX system run.
For the zip file: unzip calendar.mods.zip
For the tar file: tar -xvf calendar.mods.tar
On other sytems, you're on your own.
5) If necessary, chmod the new calendar.cgi and the Calendar_art directories to 755.
The calendar.mods.tar file contains the modified calendar.cgi, this readme file, and six directories of images that may be called by the calendar and used for navigation buttons and month names.
There are three typstyles contained in the archive: Calendar_art, Calendar_art2 and Calendar_art3. These directories contain non-transparent type with drop shadows on white backgrounds. If you want to use a different background color for your calendar, you'll want to use the the graphics in Calendar_art_trans, Calendar_art2_trans, and Calendar_art3_trans, which have transparent backgrounds, but no drop shadows.
The graphics are provided as a courtesy - I expect you'll have your own ideas about what looks good on your calendar. Creating the graphics should be done in any paint-type program that allows text entry, and can save in gif or jpeg formats. The modified cgi defaults to the gif filetype, but can be changed in the variables declaration section. The names of the graphic files should be EXACTLY the same as the provided examples, or you'll have a little modification to do in the cgi to make it recognize your file names. The simplest thing would be to name your files just as I have so that when the script looks for "January.gif", it'll find it.
For the modified script to run without change, keep the graphics directories at the same level as your "Databases" and "Library" directories, that is, at the same level as the Calendar cgi itself. Some servers refuse to serve graphics from the cgi-bin directory. In this case, place the graphic directories in an area outside the cgi-bin directory and adjust the calendar.cgi accordingly. The path to the graphics is set up as a variable in the cgi and can be easily changed.
I really don't think anyone will have much trouble getting the modified calendar to run, providing they already have the original version running and properly configured. It's probably not a good idea to start with the modified code, just to keep things simple at first. Whatever configuration changes are required for the modified version should be covered in the cgi comments.
Finally, I have tried to add comment lines marking my modifications, and have tagged the mods with either my name or initials. If you make any changes or enhancements to the cgi, you might consider doing the same so we can keep track of the revisions.