You can create collection thumbnails using any image-editing software, for example Photoshop or Sketch. If you don't have access to such, you can use a free or paid online service such as Canva or PosterMyWall. Choose an image, typeface and text/background colors according to the company’s Brand Guidelines.
For more information, you can download our Thumbnail Creation Guide here.
You can also use our templates for Adobe Photoshop/Adobe Illustrator or Sketch: