First of all, a clarification: a MOD is short for a MODification to the game. It includes new .TBL entries for weapons, ship retexturings, etc. A "model", on the other hand, is a newly created and modeled ship. Now I know that we have slipped into using "MOD" as a catch-all, but it's inaccurate.
So with that as a basis, I'll say this: there are
plenty of MOD's for download, and the HLP staff is working on a whole new MOD database including many new MOD's that have been submitted but not put into the old database. However, new ship models are for the most part like what delta_7890 said: made for campaigns and such.
Personally, as soon as the
GVCa Amaunet is ready, I will release it to the public. Same goes for the
GTExD.

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Creator of the
Sandvich Bar, the CapShip Turret Upgrade, the Complete FS2 Ship List and the System Backgrounds List (all available from the site)