Or, more accurately, I could agree with it under certain provisos. The first is that Star Wars is well suited to it because Star Wars is already a chameleon. Already, it is little more than a swords-and-sorcery Fantasy adventure in Sci-Fi drag. One can certainly switch out one man-sized sequined dress for another. The second is that it depends on one's definition of Steampunk. If Steampunk requires an element of "rebelliousness" - just against something regardless of what - and a questionable fetish for weaponry, then Star Wars would be the superior choice (though a Steampunk version of The Matrix would also suffice). A franchise like Star Trek, on the other hand, would lend itself better to a Retro-Victorian, Voyages Extraordinaires reimagining because it already features more expansive themes of exploration, science, technology, culture and encounter with The Other. It would not take much more to imagine the starships as ironclads or the United Federation of Planets as the United Kingdom of Planets.
Nevertheless, while no formal attempts have been made to Steampunk Star Wars, since George Lucas is content to allow the franchise to suffocate in an officially licenced "Expanded Universe" without confusing it with alternate versions, the years have seen many different renditions. Among the first was Eric Poulton with his pencil drawings. Below you see Lord Vader and his Death Star. More are available, including desktop wallpaper versions, at his weblog.
Dimensional artist Sillof created a whole army of custom action figures featuring his ideas. Unlike Mr. Poulton's, Sillof's draw a great deal of inspiration from the Middle Ages in its imagining of the Jedi and Sith. Below are smaller resolution photos of the Rebels and Empire, while you can find better photos for A New Hope, The Empire Strikes Back, and Return of the Jedi at his website.
The CGSociety: Society of Digital Artists held a contest for computer generated characters. The result was a more thorough exploration of ideas attached to the concept. Two of the winning entries are presented here, gratuitous cleavage included, and the whole assemblage can be viewed on their forum.
Greg Peltz tried something a little more straightforwardly Victorian and Star Warsy with his portraits of the characters. C3P0 is below, the others can be found here and here.
Mattias Adolfsson went one step even further back from a Victorian version of Star Wars to a Baroque one. His whimsical, cartoony style is pitch-perfect nonetheless, and my favorite example of this aesthetic exercise. Visit his weblog for more.
None of this, of course, settles the issue of which is better: "Steam Trek" or "Steam Wars"?