We used to have Rei's Minimap as an allowed mod, as you can see
here. However it became unsupported, was hijacked, and, as a consequence, it contains added features that we do not allow. This mod is very similar to those hijacked versions of Rei's Minimap.
From what we know, currently there is no good minimap mod, however we suggest you use
Dynmap since it pretty much updates quickly, shows your claim and builds, including in 3D, and shows your location, which are pretty much the features we allow if there was a decent minimap mod for our server.