Well, we finally figured it out.
We have a blue Crossfit so we started with all of the names for the color blue and things that are blue, like Azure, Bluebell, Indigo...
Or names that recall an evening sky, like Starry Night, Stella, Nocturne, Polaris...
But then we started talking about how everyone (including us) wants their van to be bigger on the inside than on the outside: "I want a full kitchen, recliner, big screen TV, soaking tub and two king-sized beds...while still being able to park in a spot at Walmart marked "compact"...
Well, after thinking about it, we decided our van really IS bigger on the inside than the outside - after all, they fit a WHOLE HOUSE in there (kitchen, bathroom, bedroom, living room, dining room)...
And, furthermore, after we've spent a few days in it, we feel like we're getting YOUNGER...
So we are pretty sure we have stumbled across a Time Lord's TARDIS.
So THAT'S what we're going to call it.