Depends on the "Age" of DC comics you read... in Golden Age/Silver Age (40's to mid-early 70's) there was Argo City.. or the city in a bottle. Depending on the time, it was either free floating in space, or shrunk and in a bottle captured by Brainiac 5. This is supposedly where Supergirl was from. And then you had the Kryptonians trapped in the Phantom Zone.. these were basically mostly criminals, though you had some in there who had escaped the destruction of Krypton in that fashion. The whole of Kryptonian government had that given as an option to escape the desctruction once that became clear it was going to happen.. but it was either too late, or they wouldn't be locked in for all eternity with murderers and such.
Later on, that all got changed of course. Several times.. which is kind of when I stopped reading comics.
Read some Superman "post-Crisis" but when they "reinvented" Superman as a yuppie, that kind of did that in for me.
Was always more of a fan of characters like Swamp Thing, Phantom Stranger, Hal Jordan's Green Lantern and Deadman anyways. (grin)
(which reminds me, and is kind of relevant)..
Have you guys considered the possibility of playing with Freedom Force meshes to build your Kryptonian "fighters"? Was playing with them a little bit when Kane asked me last month to help him with an avatar for FF and put together some characters such as so:
As you can see, these meshes would work.. but you'd have to find some way of converting the NIF files to SFC (unless you can find Max files already). And these are NIF 4 as opposed to NIF 3 like BC. But if you can find the Max files, or find a NIF importer that'd work with these, it'd make things a lot easier for you. And look better as well..