The html WorkBook login screen will from 9.4 support full screen pictures.
While they have always been small or scaled down for the silverlight version, they will now cover the entire browser window. This means that when upgrading to 9.4 or beyond, you might find that your login screen has a very stretched and pixelated image.
This guide is here to provide the optimal dimensions and format for your log-in screen image, as well as instructions on where to change it.
Dimensions & formats
Gif (yes you can have an animated gif in your login screen, but you should stick to short gifs)
Optimal: 1024 x 799
Other dimensions can be used, but the image will be scaled down or up. Scaling up is what causes the stretching, so smaller dimensions should be avoided.
Downscaling happens when the image is wider or taller than optimal. It can mean that only part of the image is shown as the top and bottom gets cut off, but the part that is shown should still look good.
The setup is (currently) only found within the silverlight version, under Global System Settings -> Log-in customization: See below.
The setup page joins the html version in version 9.5 and will also feature a preview so that you can see beforehand if the image is stretched or pixelated.
Examples for comparison of old & new