Just to be clear, when you say "It can be left like it is, since it links to this forum." you mean the statement giving you credit can be left as is, correct?
Also, are you okay with the wiki using the full-sized version of the map as opposed to just the thumbnail size that was uploaded by the wiki user Layarion?
Lastly, when you say "But it would be nice if you could delete the old maps", which old maps are you referring to? The old versions of your map?