A background image in the forum must be at least 2000 pixels wide and at least 1000 pixels high, but the bigger the better.
The size of the image file can be a maximum of 2.5 MB.
The image is centered in Kundo, so if the image is too small, it is hidden and ends up behind the forum itself.
In Arla's forum you can get some inspiration from their beautiful background image.
If you do not want a full background but instead an image in the header (on the top of the background of the forum), the image must be at least 2000 pixels wide and approximately 250-300 pixels high. A higher image will be cut off against the rest of the background.
We really like the way that the Swedish Kennel Club works with a header in its forum.
Bookmark image (favicon):
A bookmark image is what appears in the tab of the browser when someone visits your forum. For this you can upload a small picture, usually you already have one on your website that you can use. If you do not have access to that image yourself, consult with your webmasters and they can help you.
Here is an example of a bookmark image: