I would love to have the nemesis Romulan uniform, I'm not a fan of many of the choices we have currently.
More Parts for the Tvaro. I love the design, but I like to mix things up a little.
Romulan ship decals. The Federation has theirs, you can change it for your fleet insignia. The Klingons have theirs. I would love to have the Romulan logo appropriately placed on the head (beak ?) of my Romulan D'Deridex.
While on the subject of ship decals, I would love to be able to put the old bird of prey decal, the one you used to see on the bottom of the old style warbirds, on some of the newer designed ships. I think it would look haawwwt http://www.myspacemuseum.com/decals03a.jpg