If you've got the running lights, then you've got the model. What's happening is you've got missing textures. You should have them (there isn't an orion version out there to my knowledge that doesn't use the standard maps) but for whatever reason they aren't loading properly. Can you get us a screenshot of the problem, by chance? And your command line options would be useful too.
I can't get a screenshot at the moment, although I should be able to grab some tomorrow if you still want them. Like I said, all I can see is the rough outline of the destroyer formed by the lights, targetting still works fine, and it still fires at me normally etc. I've copied the contents of my launcher.ini file below, the command line options are there:
[launcher]
exe_filepath = J:\Freespace2\fs2_open_r-P420060323.exe;
game_flags = -spec -glow -jpgtga -mipmap -nomotiondebris -2d_poof -cache_bitmaps -missile_lighting -targetinfo -orbradar -rearm_timer -3dwarp -warp_flash -snd_preload ;
active_mod = mods;
I'm using OpenGL @ 1024x768x32 if that helps. If you think it's just missing textures I'll try clearing out my FS2 directory tomorrow, it's getting a bit messy and I've installed a lot of stuff in the last day or two, so I've probably caused it myself.