This is a fairly simple rule, with instructions. What happens when you upload a photo and there's already a photo with the same name? Simple: you rename your photo. Failure to do so results in a ban.
Uploading a photo with the same name
This is only to erase if the photo is yours. Example:
This photo is mines, so it's okay to overwrite it. I can always re-upload it. However...
The photo at the bottom isn't mines. Sure, the one with this blond is mines, but the other isn't.
You DON'T click "overwrite the existing photo with yours" unless the existing photo was already yours. You rename your photo.
Then, when that's done, you press insert. I doubt, highly, that there would be a page with the same name if you put your name next to the original name when you rename the photo (wow, that's a lot of names XD)
Ban
This is still under debate, but I'd say that this is the basics:
First time- Warning
Second Time- 1 day ban
Third Time- 3 Day ban
Fourth Time- 1 week ban
Yes, this is that serious.