This cel is from the very end of episode 26. At first I thought it must be from cut footage, since it didn't quite match the sequence in the episode. Then Kenneth Lee submitted to Anime on DVD a screencap gallery from the ending credits/epilogue of the Japanese release of the last episode. This "where are they now" segment was cut from the US release, which simply puts the very final screen up in one corner and runs the credits on a black background.

Anyway, down at the very bottom of the screencap page you'll see something very much like my cel! Back on earth all is (sort of) peaceful again, and the three friends race towards their "goal". :-)