Below you will find all the information you need to create Gif banners

1) Open your favorite image editing software (for e.g: Adobe Photoshop)

2) Just create a new document...

...with one of the allowed sizes (125x125;300x250;468x60;728x90;120x600;160x600).

3) Free your imagination and your creativity!

4) Export your Gif banners

 At the end you have to export and optimize your Gif banner ("File > Save for web" with Photoshop) in order to have a light weight (should not exceed 15 Kb).

Few examples: