There's no rule at present against putting alternate or deluxe covers on, as you term them, "standard" album pages. Many people scrobble album titles without the additional edition information in the name, so it's fine for all of the different versions of the cover to be on the album page that has the title alone. Also, sometimes the track list in the catalogue isn't necessarily for the standard edition of a release.
Theoretically, the most popular and desired version of an album cover should rise to the top, although yes, some users probably do game the system. (If users do this with extra accounts, they're risking being banned, so I'd suggest not doing so.)
Unofficial covers, on the other hand, shouldn't be uploaded. However, there isn't really a system for reporting such covers on the moment, only obviously abusive covers (which you can flag on the page). It's been previously suggested by users that there should be an option to report incorrect art too.