You can use almost any photo (or image) that you like to set as a Home or Lock Screen Wallpaper. The method to do so is outlined within the iPad User Guide:
Change the wallpaper on iPad - Apple Support
You should note, however, that a Home/Lock Screen wallpaper image cannot be directly extracted from the iPad. If you can kept the original image (perhaps in your Photo Library or elsewhere), you can use the image again - but it is simply not possible to extract it from iPad Wallpaper settings.
If you not kept a copy of the original image, you'll not be able to recover the image directly from your iPad. However, you might be able to retrieve most of the image by taking a screenshot of a Home Screen page that you have not installed any Widgets, App or folder icons. The screenshot image can be cropped, if necessary, to remove borders.
Take a screenshot on your iPad – Apple Support