Means the path to the image is invalid, usually. Or the image file itself is invalid.
If you had your own logo, you might have placed it in the TD's install folder, such as:
C:\Program Files\The Tournament Director 2\images
But with version 2.5.5 and later, the TD now looks in a different place to find stuff. By default, it's a folder in your "My Documents" folder. On XP, it would be:
C:\Documents and Settings\<your Windows login>\My Documents\The Tournament Director 2\Data\images
Or, just:
My Documents\The Tournament Director 2\Data\images
On Vista:
C:\Users\<your Windows login>\Documents\The Tournament Director 2\Data\images
or:
Documents\The Tournament Director 2\Data\images
So, copy the image file from the TD install folder to the new data folder in your "My Documents". Hopefully that's the issue.