When using images, use the highest quality available. Whether in your PowerPoint, on brochures, or on your web site, there are free sources of high quality authentic images available.
In addition to copyright laws, it is equally important to pay close attention to the applicable terms and conditions of copyright free images.
Magazin Deutschland allows you to use their images free of charge.
The reliable Tatsachen über Deutschland is still a great source for information and images.
CAPL has over 2500 high quality images of Germany that you can use on your Facebook Page, print on posters, or put on your web site, all free of charge!