Many people frame their cels... try doing a 
forum search for previous discussions about it, 
since no one seems to be answering this post of 
yours. :)  I don't currently have any framed, 
but I am about to frame two of my favorite/most 
expensive cels.

You shouldn't store sketches in the same bag as 
the cel unless they are already stuck, so if you 
don't know if they are stuck, I would recommend 
checking it out and removing the sketch from the 
bag if it is not attached yet.