It's worth mentioning that you could also remove lock screen ads by disabling your lock screen altogether, but the risks far outweigh the benefits, so you really shouldn't do this. (android.gadgethacks.com)
You can display a full - screen ad while a Web page or app is loading. (scientificamerican.com)
Yes, lock screen ads — as in, your phone becomes a pocket billboard every time you turn it on. (businessinsider.com)