Well, here are the StarFuries Thunderbolt and Escort Aurora:
16 (List/Detail view on Explorer)
32 (Standard size desktop icon, small icon view on Explorer)
48 (large icon, IIRC)
64 (larger icon, d'oh)
128 (preview icon size? I dunno, largest that WinXP supports)
256 (Vista, Macs and *nix's can use these giants)
Heh, nice squadron formations by the way...
I think the Aurora is better for a Babylon 5 game icon. It is, well, more iconic considering the show; Thunderbolts are awesome but Auroras saw a lot more screen action in the series and just for that reason I think either Aurora or the B5 station itself would be better than the Thunderbolt.
In a contest between B5 and Aurora, the StarFury stays better recognizeable and fills more of the limited space of the icon, but it's your call.