Just in case you do not know (ignore this if you do)
Screenshots are saved in your Trainz User Data Folder which you can locate from the Trainz Launcher --> Trainz Settings --> Install Tab. Copy the location details shown and paste into the address bar of Windows File Explorer. When the folder opens one of the sub folders will be Screenshots. Open this folder and identify the image you want.
In Win 10, open Settings --> Personalisation --> Background. Set the Background drop box to Picture. Click Browse and open the Screenshot folder you identified above. Select the image you want.
