Hmm, this is one of those interesting questions.  
I myself feel that if you havent seen a show or 
dont like the show that you shouldnt go after the 
cels like mad, but I think it's okay to want one 
or two.  I have a couple cel friends who dont 
really care for anime, but they're avid anime cel 
collectors.  They like it, but they're not otaky 
by any means.  They collect simply because they 
like the art in the cels.  This bothers me a tad, 
but not enough to think it about more than once 
in my lifetime.  To each his own.  

Now, there are people out there who dont like a 
character or show at all, maybe even hate it, and 
they still go after the cels because they're 
status symbols, or they know others want them.  I 
think people who do that need to have their 
booty's whipped.  

As for if I do this...I do not buy cels from 
shows I havent seen.  Mainly because if I do 
that, and something I want really badly comes up, 
I will resell the cel I bought from the show I 
havent seen very quickly.  That makes for a lot 
of scrutiny...plus, the cel should have gone to a 
fan in the first place ~_~.  I agree with you 
that I think a real fan of the show or character 
deserves the cel more, which is why I dont own 
any Hotohori or Kenshin cels...I like them, but 
not a lot.  Also, I have some Ayashi no Ceres 
cels...I didnt like that show very much at all, 
but the characters were likeable (some of them), 
and Im a big fan of the artwork.  BUT...if you'll 
note, I am only going after a few cels of the 
main characters.  I wont go for any more than 
that, or cels that are uber key scenes.  I just 
want nice face shots of them.  While Im not a fan 
of the show, I am a fan of the creator's art, so 
that's a bit different.  Im not hoarding ANC 
cels, because I know there are true fans of the 
show who I think should be the ones to have the 
best ones. :)  It all depends on what one's 
motives are when buying cels.  I tend to stick to 
the three shows I like enough to buy art from, 
and even then only key characters.