File Naming
First, in Typepad, when uploading files to the file manager (Control Panel, Files) you CANNOT use spaces or other funky characters (although underscores are permitted). So for example, if you created an image for the Birthday Promotion. You cannot upload the file with the name "birthday promotion.jpg". Instead use "BirthdayPromotion.jpg" or "birthday_promotion.jpg".
HTML or Hyperlinks
When creating hyperlinks or creating sidebar image/links in Typepad, it is important to remember that "the file name is case sensititive."
For example, if we were creating an image link and using the image called "BirthdayPromotion.jpg".
In this example, this format would be CORRECT.
<img src="http://blogsbyheather.typepad.com/BirthdayPromotion.jpg">
If instead you used the following (INCORRECT), you will see an X for an image place holder. Againg the name IS case-sensitive.
<img src="http://blogsbyheather.typepad.com/birthdaypromotion.jpg">
Hope this helps!