Hehe, preaching to the choir buddy. I've drawn a gajillion OS-tans, including all variants of DOS-tans that are all pretty terminal-like themselves (and of course, the goddess System I UNIX-sama). ^^b
Ironically, I've drawn just about all except Vista, because honestly another Vistan isn't needed (there's about 1,423,644 variants of her already, ugh). Better to focus on OS-tans that haven't been properly represented yet. -v-
Appearances matter, true, but so do references and context too. Otherwise, no one would ever know that Inu-T and Saba-chan represented Windows NT and Windows Server 2003 respectively without knowing a little bit more about the culture of canon OS-tans. Similarly, only a handful of those Vistans actually look like the main Vista interface (I imagine the one you're thinking of is included here) -- the others are hodgepodge of botched ideas and internet memes scattered all across those image boards.
Likewise, one really should read Ubunchu to get the context of the dress too. -v-
But as you say, a CLI-tan should be inherently flexible, and capable of switching colors on the whim. I use a gray and green termial, for example. Standard *buntu users have white on black. And of course the debconf terminal window is of course... *drum roll* ... blue and red! LOL. XD
So yeah, let her be able to change into different dresses -- maybe each one gives her a different power. ^^
Oh, and also.... it was technically Risa-chan who drew CLI-tan. hehe.... ^______________^