Unfortunately Escaflowne cels are becoming rarer 
(like most older, cel based shows! :( ), 
especially the nice ones...  Right now, Yahoo 
Japan and eBay combined only have two, both TV.   
The only movie cels of Hitomi I can recall offhand 
are the ones at Animanga and Anime-Museum.  As for 
Van, there was a fairly nice profile of him 
fending off Dilandau's sword and one of him with 
wings and Hitomi a couple weeks ago on Yahoo 
Japan.  I don't think anyone bid on them.   There 
might be more at the other online shops, but I'm 
sure you've looked through most of them already.

I'm looking for movie cels too, just landed a 
Jajuka (only really need TV ones of him now...hah!
) and am searching for just one pretty good movie 
Dilandau, so I'll definitely keep my eye open.

I almost wish I was interested in Hitomi and Van 
like you are...relatively, it would be much easier 
to find "fairly decent" cels.  Nah nevermind,
there's just something about furry and insane 
people...  :)

Best of luck to you in your search!