Although I appreciate that you've been trying to help in providing Nickelodeon Magazine covers we don't already have, those last five covers you uploaded aren't actually real. Those were fake covers that were made up specifically for a puzzle in the magazine's "fifth birthday" issue in June 1998; they're clearly stated as such in the "answers" page at the end of the issue, a scan of which I've provided right here.
This is a duplicate of the message I left for you on the SpongeBob wiki.
Nickelodeon may have had plans to release a sixth volume in their "Nick Picks" series and even went so far as to make cover artwork for the DVD, but they do not appear to have actually manufactured this product. Please do not try to invent information about what might have been on the DVD. It's just another example of a company that planned to do something and then changed their mind.