Unless i missunderstood you,
This should be easy to do without using a plugin…
Embed this in your functions.php:
function echoDayImage() {
// GET CURRENT DAY
$currentDay = get_the_time('l');
// CHECK DAY AND ECHO SUITABLE IMAGE
if($currentDay = 'Sunday') {echo TEMPLATEPATH.'/images/Sunday.jpg';}
elseif($currentDay = 'Monday') {echo TEMPLATEPATH.'/images/Monday.jpg';}
elseif($currentDay = 'Tuesday') {echo TEMPLATEPATH.'/images/Tuesday.jpg';}
elseif($currentDay = 'Wednesday') {echo TEMPLATEPATH.'/images/Wednesday.jpg';}
elseif($currentDay = 'Thursday') {echo TEMPLATEPATH.'/images/Thursday.jpg';}
elseif($currentDay = 'Friday') {echo TEMPLATEPATH.'/images/Friday.jpg';}
elseif($currentDay = 'Saturday') {echo TEMPLATEPATH.'/images/Saturday.jpg';}
}
Then in the location you wish to use it just use the function:
<?php echoDayImage(); ?>
(learn more about formatting date / time here: Customizing the Time and Date)
EDIT 1 (for comment explenation)
function echoDayImage() {
// GET CURRENT DAY
$currentDay = get_the_time('l');
echo TEMPLATEPATH.'/images/days/'.$currentDay;
}