The Throwdowns are still fun, at least as far as I am concerned. Phil, if you put somewhere in your original post that it is an older photo and posted as a joke, then I see no foul, and no need to remove it.
I am probably going to add a couple rules to the Throwdowns along the lines of the following. This should hopefully address these areas, which have become a problem of sorts...
Editing others photos AFTER they post them should be discouraged for the reasons Rick gave. When people see an entry posted, and then after that entry is posted someone alters it and reposts a better version of that picture, some people think that is unfair unless they do that to EVERY photo. So don't do it. If you want to edit someones photo, or have someone else edit your photo, then do that before you enter the dang photo. Don't go posting 2 or 3 different versions of the photo, that makes it confusing.
Also, we have seen some good joke photos posted before and that helps to keep this fun. Please try and point out that it is a joke photo though. If you do not, i have no choice but to assume it is a valid entry. I made the mistake once of assuming someone posted a joke picture and left it off of voting, only for that person to feel slighted. So either explicitly state that it is a joke photo, or don't post it.
Now, back to the fun!