I notice that for one of your comics you're using a template you made yourself and attempting to link to an image that resides on your own hard drive. This is impossible, you must upload the image to the web somewhere and then link to it. The "files" section of your comic control panel, Imageshack.com, or photobucket.com are all good places.
Another easy way is to include this code in your template: <!--[COMIC_NAME_IMAGE]-->
Then upload a title image for your comic by using the form in the first section of your comic control panel. If you have trouble doing that there are some work arounds discussed here: http://www.drunkduck.com/community/view_topic.php?tid=30581&cid=231