Hmmm, some good questions . . .

1).  A (A little), in some cases B (A lot)
2).  C  (Decreases value unless you can remove it)
3).  A  (A little), sometimes B (A lot) depending
on the scene or character.
4).  B.  I would personally pay more for a cel
with background than one in the same sequence
without one.
5).  C (decreases value).  To me, anything stuck
decreases value.  It shows signs of damage
especially if you try to remove it.
6).  A  (Increases value a little).
7).  C  (Decreases the value).
8).  A  (a little more valueable).
9).  A  (little more valueable), or B (depends on
the character(s) or scene).
10). B  (a LOT more valuable), but C (depends on
the cel).
11).  A ( alittle more valueable).
12).  B  (increase value a lot).  Normally the
cels I frame are the cream de la cream ($300+
value) and the frames themselves cost almost $100.
13).  A  (increase a little) or B (increase a lot)
depending on what scene it is.  If you can verify
a high end cel is 100% original with a screen
capture, then chances are it will sell for more.

Star Phoenix