Oh great, there is some help

I haven't placed a character yet, i just wanted to set the first scene bevore placing a character and everything else. (Maybe because i went throught the handbook step by step and setting the background was the first stop, hehe)
I don't want to start the game rigth now but i just wondered why noting happens at all when creating a background for my scene.
Here is what the log says : Error reading header from image Testgarten2.png
I guess this is the Problem but what could it mean?