The WAR file does not include the new background images.
For the background images, create a directory named "custom-pisasales" on the Tomcat, as a sibling of "cfg-pisasales", "app-pisasales", etc. In the "custom" folder of the web app ("custom-pisasales", "custom-pisatest", etc., depending on how the web client is deployed) create the folder ".../bkg/random". This is where you can place the images of your choice. If this folder does not exist, then the monthly images will be displayed as before.
In the "custom-<webapp>/bkg" folder, other monthly images following the naming convention "bkgxy.jpg" ("bkg01.jpg" for January etc.) can be stored as default backgrounds for the web client. If you store only one "bkgdef.jpg" file there, it will be used each time.