1. you have one jpg-file
2. give you that jpg-file the name "background.jpg"
3. copy this jpg-file into your folder: G:\program\steamapps\common\RailWorks\data\texture s\frontend\
4. click with the right mouse button on the background.jpg and look at the properties of that file.
5. select the option "write protected"
6. start the game and see your new background
If you have not a background.jpg you can download this background.jpg and save it in your folder G:\program\steamapps\common\RailWorks\data\texture s\frontend\
http://www.klemund.de/RailSimulator/...background.jpg