Do dynamic wallpapers drain battery? Is it true that using a dynamic wallpaper will drain the battery faster than a still wallpaper? If so, how much faster does it drain?

(I'm using an iPad Air running on iOS 7.1)
In general, dynamic wallpapers drain the battery faster than still wallpapers. The amount of drainage is dependent on the wallpaper itself (whether it has many bright colors, is graphic intensive) and how it's programmed (CPU and memory usage, etc.). There are ones that are better than others. Also, how often are you on your home screen where you see that wall paper? Obviously it will only affect you battery life if it is on the screen, so if you are using apps all the time you should see virtually no difference. I would suggest experimenting with your iPad's battery life with a dynamic wallpaper and without, and see how they vary with your usage.