Here is a quick little mod I made today to Sources/Calendar.php to display an image above The recently added Calendar feature to YaBBSE.. heres an example pic from one of my sites with the mod in action :

The mod allows you to create an image directory where ever you would like to keep your Piccies for your calendar in. The Images are indexed by "Monthyear".jpg (.gif / .png if you wish, just change the .jpg extension in the code) such as April2002.jpg.
Heres all the code you need..
find:
// Save some processing time by only doing this once. Particularly if the "Days as Link" option is
// turned on.
$bCanPost = CalendarCanPost();
print "<table border=\"0\" width=\"100%\" cellspacing=\"0\" cellpadding=\"0\" class=\"bordercolor\">"
Add after:
// Miskie's Calendar Image Hackery October 22nd, 2002
print "<td align=\"center\" colspan=\"2\">";
print "<img src=\"http://your.site.com/calgirls/".$months[$month].$year.".jpg\" border=0";
print "</center>";
if any of you feel so inclined to make an admin control panel for this, be my guest.
I applied this to a heavily modified 1.4.1. without an ounce of trouble..
** This mod ASSUMES you use only one language on your board ** since the image name is derived and not hard-coded (to allow you to add as many as you like) a non-primary language user will not be able to see your images, unless you make renamed copies for them as well, or write a whole bunch of extra code.. Im too lazy to go thru that much work

**