Given the scarcity of documentation that ships with the iPad, apparently Apple thinks all operations on the iPad are intuitively obvious. Consequently, I felt like a fool when I was wondering how to turn my pictures into wallpaper. Part of my problem may be that I decided to not synchronize pictures from my Mac to the iPad in order to save storage space. What I wanted to do was open my Flickr account, select one of my pictures, and use it as wallpaper.
When I browse a picture in Flickr using Safari, and either tap or tap and hold on the picture, nothing happens. I was expecting to see a pop-up menu with an option to use the picture as wall paper like I can do on my Windows desktop. After some trial and error I found that I had to tap All Sizes, which is above the picture, that then shows a Download link at the top of the page. However, tapping the Download link also does not work, but on the Available Sizes page you can tap and hold on the picture and a pop-up menu displays with Save Image and Copy options. To save the picture to your iPad tap Save Image.
At this point there are two ways that you can make a picture the wallpaper on your iPad. You can open Photos, tap the picture, tap the share button at the top right of the screen and tap Use As Wallpaper, as shown in the picture below. You can designate whether to use the picture as wallpaper on the Lock Screen or the Home Screen, or both. The second way to select the picture for the wallpaper is to go into Settings, Brightness & Wallpaper, tap the preview of the current wallpaper, tap Saved Photos, and then tap the picture.
On most other web pages that have pictures, you can tap and hold on the picture to display a pop-up men with a Save Image option. If you do a Google search for iPad wallpaper, you will see many options for wallpaper including www.ipad-wallpapers.com.